Those who switched PIs- how did you know when to call it?

I'm exhausted and don't really know what to do. My PI is a fairly new TT professor at my R1 university and since then, has "lost" I think around 5 students. I was a direct admit to his lab because I was really interested in the research topic and had no idea about his issues with other students.

The spring semester was great, totally fine. He didn't allow me to do much experimentation and had me write a bunch of stuff for publication, though. When I had classes to attend/teach it was good, but this summer has been absolutely horrible. I've realized now that I'm doing experiments, that he is an INSANE micromanager, watching and taking over everything I do. I thought at first its just because I'm new (although I have extensive lab experience), but even when I've been trained 3+ times on something, and I know what I'm doing, he's watching me and taking things over without warning. He won't allow me to learn. There's NOBODY else in the lab. Just me, the lab manager (his wife), and him.

Things have been more tense since I've started pushing back a little on things, trying to have these conversations with him. It really came to a head last night. He was spamming my email, requesting edit access and rewriting my qualifying exam at 11pm. It was due at midnight and had been finished.

I don't really know what to do. If I leave, I'm essentially ruining him. His tenure will probably be sunk, and he frequently calls me the 'hope' of the lab for this reason. He's honestly a really nice guy (I know I didn't make it sound that way, but he is, he's just very neurotic). Plus, I don't want to lose the progress I've made in the last seven months by starting all over. But if this will be how it is, I don't think I can do it. I can't tell if its because of the summer, when I'm around all the time as opposed to taking/teaching classes, or because I'm now at the point of really starting my research.

EDIT: I just found out by talking to a previous student that he made an entire powerpoint about the students before them, and that when they discussed leaving after their rotation, he tried to guilt them by saying he has cancer (which I have never once heard, and I have no clue if that's even true or not). Despite railing on all the previous students he always say he would take any of them back if they wanted it. I'm...a little shocked, and now I really have no clue what to do.