It still kills any campaign in a competitive race that isn’t Trump’s.
I have doubts. If you're a Democrat yes but a Republican no.
I wouldn't be too sure about that. We've already seen that Trumpism without Trump simply doesn't work. Just ask Mastriano, Majewski, Lake, Masters, and every other ultra-MAGA, 2020-denying Republican who said batsh**t crazy things on the campaign trail and suffered noticeable electoral consequences for it
Trump has a very odd appeal that grants him the immunity to say and do whatever he wants without suffering any significant political damage; an appeal that hasn't been replicated by any other Republican politician yet. It would be a mistake to assume that appeal has extended to the entire party when it evidently has not.