Or maybe he just doesn't have the skill and control to handle that much power without getting injured, physically or psychologically.
Quite possibly - in Changes, after Harry uses the big ley-line powered gravity spell to kill a ton of blood-crazed Rampires, he tries to 'reach out with his will' to it again and gets freaky sensory feedback and mental pain. The Demonreach ley line might have similar effects amped up to a level that would leave lasting damage.
And the Gatekeeper says he's "years away" from being able to do it safely, which implies that it
is possible - if it essentially shoved a chunk of dark power into your soul, like black magic corruption or a non-Outsider-linked Nemesis, I think that would change you regardless of how experienced you are.
Well, for one thing, saying that the winter mantle does not help against will attack is untrue.
Oh, I think it does help somewhat - when confronting the Lords of Outer Night at the sacrificial altar, he talks about pushing back with his own will and Soulfire and Winter. What I think is misleading is that Bob seems capable of providing essentially
total protection, as do the Swords, whereas the Winter Mantle only helps a bit and wouldn't have been sufficient by itself (in that scene, Harry pushes back, but doesn't break free until Lea kills 2 of the LoON and distracts the rest).
Well, Harry ask for overt help like sending an army of einghenjars and Valkyrie. I am certain that Odin is sying the truth when he said he can't grant that kind of help.
I really, really doubt it. Odin can hire Valkyries and Einherjar out to random people like Marcone -- he had Gard working for him way before he had Accords status. So it doesn't seem that any special god-rules limit his ability to send Valkyries on missions.
If you think it through being the winter knight is great for Dresden.
Everyone gets way to hung up on Mab being unlikeable and ignores the big picture.
I totally agree the missions Mab's sent him on were all beneficial things. Harry does seem to view Mab's actions and goals more negatively than the facts really bear out (probably because most Winter Fae
are cruel, vicious, and/or prey on humanity ... Mab is occasionally cruel about minor things, like the ice-in-Harry's-eyes bit in SmF, but mostly she's very much "cold calculation".)
However, the big issue with being Winter Knight isn't so much Mab being unlikeable/cruel as it is the corrupting influence of the Mantle itself, though. It often doesn't really seem "worth" what it gives Harry, especially since it comes with the iron weakness of the Fae.
It definitely gives him some physical advantages... but frankly he seems mostly less effective in CD and SG than he was in TC and the early part of Changes, when he had all his gear.