I've signaled to my advisor and collaborators my intent to quit pursuing my PhD at the school I'm currently at. I essentially gave a 3-month notice while I get as much done as I can on one of our papers and train a newbie on the software I developed for our research while I find a new position, so I think I did it respectfully.
I really enjoy the projects I'm working on and the collaborators that we work with, but my research advisor doesn't seem to respect the boundaries I put in place. He loads me with many projects, deadlines and long meetings. Sometimes I have discussions with him about how I still have schoolwork and need to sleep, so I can't have long meetings every day or more than 3 projects (which is already a lot of projects relative to other students at my school, who normally only do 1, or 2 if they're ambitious) and he acts all sympathetic and agreeable during the conversation, but then later insists that I take on more projects or continues scheduling meetings every day, and pretends that we had never had the conversation when I mention it. Or he says something like "oh, yeah, but I thought you eventually agreed you could do it" when of course I said no such thing. The workload has put a serious strain on my health, and I'm beyond burnt out at this point. I had 5 projects and daily meetings once I finally quit, and gave the reason that "I'm just exploring my options," yadda yadda. I also found out after meeting one of his former students that he has a reputation for not graduating students on time, and will hold their thesis over them to keep them working for him. He's seemed dodgy when I've asked him the question, "what are the requirements that I need to achieve in order to graduate?" so this has been a concern of mine as well. He essentially expects everyone's thesis to be something like, "Explorations in [our field of research]" and have numerous projects in one thesis. One guy worked on, like, half a dozen papers with him and never graduated and is currently in debt to the school because he kept chasing losses to finish his thesis, even after the school stopped paying for him. He even expects a similar level of work from Master's students, which I started out as until months of continual pressure from him to instead do a "direct entry PhD program." The saddest part is that the department chair appears to know that this is happening and simply enables it. In fact, I even saw data from a couple years ago that he was the highest paid professor in our department while having had a "1" on ratemyprofessor for his entire teaching career. There's yet more that I could write about this advisor, but this post isn't really about him, and hopefully this at least gives the gist of why I feel that I need to leave.
The above circumstances are the reason why I wish to leave my school/advisor. But I actually love a couple of the collaborators that I've met through my lab. The subject matter is interesting and cutting edge, we seem to have good chemistry and the dynamic they have with their own lab appears great, from what I've seen. They work intimately with my advisor, though, and I'm not sure if there are "politics" that come into play when leaving your current advisor to work instead with an affiliated PI that you met through the lab you're abandoning. Would it be rude to drop my current advisor only to go directly to one of them, and what is the best way to approach this? Also, any advice on how to approach the "why I chose to leave" question without disparaging my research advisor? So far I've been going with "our lab is quite small and the workload can become busy, so I'm interested in possibly finding a research group with more resources" But my collaborators are still encouraging me to just finish my degree at my current school because they think it'll be easier than moving. Is it okay to give more details, or would that be unprofessional?
Thank you so much for any guidance you guys can offer. I'm in a weird mix of hopelessness and also excited freedom at the moment. I don't have many people in my professional network that I can lean on, so even though it feels that I have many options, it also somehow feels that I might actually have very few options.