There is a theory going around that the Red King and Pa Wraith are also starborn.

"Going around..." where?
Haven't seen it here.

... Evidence for this is a) for Pa Wraith the outsider protection thing he has. According to the theory he was a starborn of a previous cycle. Hence his expertise on starborn. He was sacrificed and came back with something extra. The defense thing he has.

Pretty sure it's wrong for Raith Père -- think I read WoJ stating that he just this cycle became aware of the whole "Starborn cycle" / Outsider thing, & decided he wanted to become a power-player, acting-upon instead of acted-upon... that's why he has such a substantive library:  he was educating himself.

... As for the Red King his entire motif just gives outsider vibes. Lord of the outer night. Anyone? ...

But it's not just the RK -- his inner circle was the "Lords of the Outer Night" (I call them LOONs)
That said, "Outsiders" and "Outer Night" may just be coincidental, or may not be -- I'm very suspicious of this, myself!  I do tend to think there's a connection, though I'm not absolutely convinced of one.

We also have the WoJ that the LOONs got so powerful because they actually were able to capture (and addict to their venom) the beings that the Mayans had been worshiping as gods.

I think the Ramp's are creatures of the Nevernever, natively; I note several similarities in the descriptions of the native-form (without fleshmask) Ramps, and the Ick... and suspect them of being related entities.

I think some long-ago Maya (or maybe Olmec... or even older) sorceror was exploring the deep Nevernever and got possessed -- or maybe summoned one, and got attacked/infected; thus becoming the Red King.  IIRC WoJ says the Red King was about 6K years old...?

How all of that might play into an Outsider connection escapes me; maybe one (or both) of my theories is wrong, or maybe it's as simple as Ramp entities being every bit as susceptible to Outsider influence/possession as humans are...

... It also explains a lot of things such as why Harry keeps getting things that whisper in his head. First Lash and now the mantle. Its Uriel helping to prepare Harry for whats to come. 

I think Lash & the mantle are both training-up Harry's willpower, yes!
But we've already seen that many Outsiders use psychic attacks, I don't think we need to look for another "possession" in the BAT:  I bet Harry has to face off against multiple psychic Outsider attacks at one time.

...  Also we presume it was magical homework they shared, it could have been a math assignment from school ...

I'm pretty sure it would have been both!   

But IIRC Harry specifically cited some magical homework, where they each did half & then copied one anothers' answers.

... For some reason Justin attempted to enthrall Elaine first, if she was in fact enthralled. Target of opportunity? As he taught them did he find her more vulnerable? ...

"Target of opportunity" works as a viable theory; maybe Justin had been looking for a "natural" opportunity to get one of them alone, and just took the chance he was given.  Maybe he even rushed his own plans a bit, noting a better chance than anything he had seen in a long while.

Honestly, though, I don't think we have enough info to make even mildly-informed guesses, only unsually-Wild WAG's.

... Here is another thing that really doesn't add up.. Supposedly Elaine stayed home from school that day because she was sick.. Harry cut class to return home to be with her..  Where did Harry think Justin would be during this?  Did Justin have some kind of day job? Was Justin so involved with his magical research that he wouldn't notice that Harry cut school? Did Justin even care if Harry cut school?  Apparently it was no surprise that Harry would cut school, Justin and "enthralled Elaine" were waiting for him with a straight jacket..  The point I am getting at is, Justin counted on Harry cutting class and coming home when he did, and then trapping him.  Would he have attempted it if Harry had not cut class that day? 

Cite please?  I recall it as Harry getting home from a normal school-day, not that he had cut class.  But maybe I misremember.

I can't imagine Justin had a "day job," though.  He wouldn't have had a mundane job, and he was intentionally off-radar to the rest of the wizarding world.

Does it matter (why does it matter) whether Justin had been planning for Harry to get home early, or just get home at the regular time?

... But was he equally tough on Elaine? We know nothing of his lessons with her.  Why weren't her and Harry taught together? ...

I think Harry&Elaine were (largely) being taught together.
They certainly shared a lot of homework assignments!

I'm sure there were some lessons specific to each of them, while the other did bookwork &c.  Their respective strengths and weaknesses differ, after all (not that we know a lot about Elaine's, but we see their preferred methods aren't identical).
 
I presume Elaine got largely-similar treatment to what Harry got; if Justin was notably harder or easier on her, we'd have heard about it by this time:  it's the sort of thing kids remember even into adulthood.

🙄 he already did technically, Demon Reach.
Tho as is usual your misconstruing a simple concept and plot twist that doesn't "govern the rest of the series", that's the greatest thing about the DF, you can enjoy it on many levels. Plus he has the time travel book last? Heh, I disagree. What I said was a tin foil theory to begin with, I literally started with an apologetic don't try because it's nonsensical. To share your doubt immediately after our ahem, history is bad taste. Opinion vs opinion that's enough said for me..
However be aware "I'm not sure" is synonymous with "I don't think". And  when people try to simply unname a theory as viable based on that.. well, the saying goes,",those who say you can't shouldn't interrupt those who already are".
And this has been a point of contention on how people come at each other from it has been the gathering of much heated debate and mod warnings for years.  Because it is not discussion, it does not promote discussion. And it should not exist here. It drives people away as is it's intention and is a perversion of etiquette, designed as such. Quite frankly, I'll go all ten rounds with anyone who disagrees and all day after. Stop trying to bully me, please and thank you 🙏
(Oh and you have no idea what the original theory was, because seven of nobody is running around when bodies are being tossed behind them to escape.. and proper etiquette would be to do as I asked previously and be curious about that)

With all due respect:  I apologize for whatever degree of "misconstrual" and/or "bullying" you perceive; none was intended.

I likewise find your reply to me filled with "misconstrual" and mis-statements as to what I had said.

I think it best not to engage further.

I think that is a bit of a toss up, those really offended can simply quit the series...

In the end, Jim's a commercial author -- it's how he makes his living.  He doesn't want to make too many of his fans too unhappy, or his book-sales will begin falling (and so will opportunities like movies or TV-series, and other ancillary income).  I don't think he's seeing that yet.

But then again... he's had zero DF novels released since he killed off Murphy, so I don't know that he knows, yet.

... Maybe that's why he has treated Molly the way he has, she remains strong, while her and Harry do have love for one another, there is no romance.

It's pretty clear that Molly is still harboring feelings for Harry; and Harry still admits (at least to himself) some sexual attraction (he may not be vocalizing it; but to Molly-the-Sensitive, he can't deny it).

So while there may not be any active "romantic relationship," there's still a background tension there (much as there was between him and Murphy, for many books).

I'll re-introduce my own WAG here... part of which is that Justin isn't (necessarily(*)) the "evil wizard" Harry thinks he is.

He's "old-school" and harsh, for sure... fastball baseballs as shield-training, &c.  But the mover & shaker in this was Mab(**).

She knew the Starborn Cycle was cresting, and that Outsiders would be making a special push.  Mab wanted a Starborn as Knight (and likely in other roles too), so she "arranged" for Maggie LeFay to:

• "discover" the Starborn cycle & hints of a "starbabe"plan
• "accidentally" meet the Leanansidhe on multiple occasions, sufficient for Maggie to think of Lea when she needed a protector for Harry

Then she stepped in when Malcolm died, to hide Harry from everyone searching (foreshadowed, story-wise, by Morgan being anti-scry'ed by Summer)... until Harry's gifts showed, and it was time to get him trained.

Then -- and this is where it gets relevant to this thread -- she got Justin to do the training (either by tricking him, or as repayment for debts-incurred); note how Justin's "harsh" training was often thematically-similar to a "Winter"-driven harsh training.


(*) Critical counter-datum on the "Justin is evil" front:  taking Kemmler's "EvilBob lab-assistant" skull as his own, hiding it from the WC (***)
(**) Mab and/or her handmaid, Lea

(***) On the third hand, I'll introduce another WAG -- Bob isn't really "afraid" of Mab/Winter; he's an active _agent_ of Winter, one of Mab's spies amongst mortal wizards / the White Council.  Justin, in this analysis, rescued the skull on the orders of Mab (much as Harry got the Word of Kemmer on Mavra's orders):  Mab got the skull to Justin so that he could get it to Maggie's Starbabe (which plan was already underway at the time of the final Kemmler-fight) in a way that didn't even hint at a faerie affiliation.

Even if she wasn’t enthralled he was planning to act against Harry.  Why… then?  Why the clumsy action with poor preparation?

I don't  think we have enough info.  Furthermore, what info we do have is highly-suspect:  every time Harry recalls the events or has a flashback, we see something very different.  We know harry was right off of a mental trauma, with consequent likely memory-issues.

Could be he was ordered or pressured to by The Walker.

He Who Walks Behind set up the whole gas station scene to test and prime Harry into violence. Walkers are major league you can't summon one easily. One just happened to be around at Harry's first true trial?

Might be the walker was already waiting in the wings and dumorne (cough kemmler cough) was under pressure to prepare Harry for it in time. 

What if it wasn't even communicated / collaborated between Justin & HWWB?  What if Justin wasn't in league with the Walker at all, but detected the Walker's arrival (much as Harry and Eb did the cornerhounds in Peace Talks) then panicked, and tried to force the Starborn wizard(s) to be ready...?