First, a little suggestion. Putting my statements in Italic makes it far more pleasing to the eye, and look far less messy.
A very fast TL;DR to your point about why being a threat to the multiverse doesn't mean 2-A AP is:
Imagine a hypothetical scenario. X has the power to kill one human, period. Doesn't matter what they do, whomever he wishes to die, dies. This is still, however, limited to one person.
X is a threat to all humans, and by extension to all of humanity, because he can inflict death upon any member of it. Whether there are 1 billion, seven billion or infinite humans, X still poses a threat to each one of them.
Bill's ability to travel between dimension trough the "foam between dimensions" that the nightmare realm is puts him in this exact situation.
I am not using the google definition of it. Your argument is flawed for several reasons, the two main one being that an immortal being destroying universes for all of eternity is more than enough to consider them a threat. Specifically, the reason you assume he'd destroy infinite dimensions is because of the "danger he poses to the greater multiverse", but it is made clear that not all of the multiverse, so why do you assume it is an infinite amount of dimensions?
I literally wrote how you are making assumptions. Both of us are, because there is no way to say the objective truth. My one assumptions is that threat is used to mean that Bill will be going around wrecking havoc forever if not stopped. Your two assumptions are that threat means infinite dimensions, and that Fiddlefords dimension is he exception to the rule. And your point about how infinite works is based on an assumptions you need to prove (ya know, burden of proof). You are claiming that any percentage (because a part of infinity can be a finite number) of infinity is infinite, by extension he destroys infinite dimensions. Problem is, you have to prove that:
1) He destroys, period. There is no statements about him destroying them.
2) He destroys an infinite number. he sole statement of being a threat doesn't mean that you will destroy or affect a percentage of something at all.
3) That he doesn't just keep ******* reality up for all of eternity, since someone destroying dimensions for all of eternity is sure as hell enough to consider him a threat regardless of him never destroying everything.
And as a bonus, by Ford's definition, weirdmageddon was already the end of the world despite nothing being destroyed.
I am refuting the very base of your argument. Your is meant to be plural here. There is one reason people are accepting 2-A, and it is Bill destroying an infinite multiverse. This is based on a statement claiming him to be a threat. I point out that the very statement on which it is founded contradicts it because he doesn't destroy the multiverse as a whole, and I also point out that it doesn't imply destruction, period. For your specific point, an immortal destroying universes one by one for eternity is more than enough to consider it a threat, regardless of it never destroying the multiverse for good.
This, again, is wrong. You are refuting the very basics of science here. In science, which is where Burden of Proof mostly originates from, if you are arguing for something and there is a contradiction to it, you need to explain the contradiction. For example, were we to find a planet that pushes things away instead of pulling them, scientists would need to prove that the planet is the exception to the law of gravity.
A more cartoonish example is saying "All gingers have no soul", then finding a ginger with a soul. Either the first statement is wrong, or the ginger with a soul is the exception. The one making the first claim (ginger=no soul) needs to prove the latter (Ginger w/ soul=Exception to the rule) to keep the first claim true.
In this case, you are making the claim that Bill destroys all of reality, except this one. That needs to be proven. Don' respond with the "part of infinity" (tough, again, percentage and not part) as I've already pointed that out above. If you have an answer for that, point it out there and let's not repeat it at nauseum.
For the last part, I am saying that he isn't destroying all of the infinite reality, so there is no reason to assume he is destroying an infinite portion of it. You seems to think that it is impossible to take a finite portion of an infinite thing, which is wrong. (It is possible that the universe is infinite, or at the very least that space stretches infinitely, but we still can take finite measurements).
I'm pretty sure I gave examples and reasoning of why I don't accept your logic. More specifically, "why would you assume that Bill is destroying a percentage of the universe?". I gave other possible examples, most with less assumptions. The above TL;DR being one of them.
"I am using how they define threat in that context" The problem here is that they don't define this. You are assuming they mean what you think. My TL;DR is just as applicable to threat, time baby's statement, the wrath statement, etc. The only thing you could argue for would be "the fabric of existence", which is then contradicted.
As for Kep's part, his argument boils down to one thing: "In-context, threat=destruction", which I countered.
