b) What happens if a PC or NPC is being afflicted by multiple consequences of the same type? Mechanically.. does it work? Do you just upgrade the consequence until you find a free one and then they are taken out? Do you assign stress instead? Regardless of the conflict source... lets say you arm is broken, then something happens to blind you, and your leg may also get broken. Am I making sense?
Yes and no. Fate is a bit funny there.
When you are in a conflict, you take a consequence in order to stay in the fight. You don't just get one pushed onto you. There are situations where the negative outcome can be pre-determined. For example if you want to jump from a moderately tall building, the GM could say "well ok, that's an athletics roll with a difficulty of 5, but if you don't make it, you'll need to take a moderate consequence, since your leg will be broken."
That's basically the only way you can take consequences, conflicts and situations like that.
In a conflict, you take stress. If the stress overflows on your stress track, you are taken out. You can choose to take a consequence and reduce that stress (for example a moderate consequence reduced the incoming stress of one attack by 4 shifts), but you can't be forced to take a consequence. You can always say "that's it, I'm taken out", and that's that. If you take 1 shift of stress and you don't have your mild and moderate consequence, and you need to take a consequence to not be taken out, you would have to take your severe consequence. It reduces the attack by 6 shifts, but since there is only 1 shift in the attack, it might be a bit overkill. And yet, sometimes you just need to do this.
Keep in mind, absorbing 1 shift of stress with a severe consequence is still a severe consequence and should be something severe happening to the character. It's not a 1 shift hit, it's a severe consequence.
I'd like to add a third question:
c) Thaumaturgy/rituals seem very powerful (rightfully I guess), as they both bake-in defeating the opposed roll (so basically skill level +4). However... this probably isn't very effective against powerful NPCs or players correct? They may be covered by a ward, happen to have a block up (fudge-spirit shield), enchanted items with blocks built in, or perhaps can even spend fate points... is that a valid understanding? Or mechanically unable to improve your resistance to thaumaturgy/ritual ... (I hope you can). This would at the very least downgrade the intended consequence/aspect/result if not cancel it outright.
A thaumaturgic ritual is, by and large, simply a scene to resolve a problem.
Take Fool Moon. When Harry tries to find out something, we get a scene about him doing a ritual to summon up a demon and ask questions.
If Murphy was the one looking for information, we would have gotten a similar scene, but with her going through Wikipedia and some police databanks in order to retrieve the information.
You can do the same here. You could have a scene with the characters fighting someone, or you can have a ritual scene to do that.
Personally, I don't think the high numbers for a ritual are all that interesting. What's far more interesting to me is having the right components at hand. So instead of saying "he's got a +4 ward around himself", I would rather say "he has a ward around himself, what are you going to do to counter it?"
If they have a vial of his blood, I'd just say the ward is null and void because of the good connection. With a piece of hair, it might be different.
Basically, set the scene of the ritual in a way that makes it awesome. Counting numbers rarely does that.
Determining whether or not you can kill someone with a spell can be done by other means. On the side of the player characters, that's usually a line that's not going to be crossed. And if it is, I will gladly accept that and explore where crossing the line leads, rather than try to figure out where to get the last 2 shifts of power from.
And after all that, I would give it a fixed difficulty. That can still be somewhat high (say 12-16 shifts), but not as high as I've seen some rituals be. Because everything has been accounted for and you can't really actively oppose a spell when it comes flying at you.
Well, unless you're a player character, then I would set up the scene for your to be able to counter it and fling the turkey into the vampire.