I just read the whole thread. Heavy stuff.
Ultimately we're talking about a constitutional crisis. There's several layers of violations, between established nat sec law, historical precedent, "what people will actually think of this". I don't feel particularly clarified.
I know this will sound super obstinate, but if legal claims boil down to "Trump, as candidate, talked to Russia", and "existence of backchannels are a legal no-no", it's hard for me to see the Trump base (and his supposed business leader death-cult) as giving any sorts of fucks.