You’re not wrong, but voting third party or no vote in the general doesn’t do anything positive for change. It’s a sad reality, but you have two options for the general, and local and state elections are where change can happen. Ideally you’d have primaries, but that didn’t really happen this cycle, although I personally don’t think it would have made a difference this cycle. Again, it’s not fair and it’s not ideal, but when life gives you lemons, you can try to make lemonade or let a fascist dictator wannabe shit in your mouth. I don’t particularly enjoy lemonade, but I’m pretty sure I would hate Trump poop in my mouth worse.
I think you’re correct, but if he becomes completely nonviable, the party will phase him out. He’s a useful-ish idiot right now. That might not be true for long, and then maybe his legal safety nets will stop protecting him once they see he can’t do anything for them.