If you are miserable in your job, and can't find something comparable where you live, go take the job your friend is offering. If you and W R, then you can figure out where to go from there, but at least you are now in the field you want to be in, rather than stuck in a job you hate.
Are they your cats? If your W doesn't want them, tell her she has until XXX, and then you are going to take them to a shelter. They are not your problem, and you are not going to accept responsibility for them. She wants the D, and she needs to accept responsibility for the consequences.
I have a very hard time detaching, and I think it's because I still see W a lot through friends and the kids. I see some of the same thing with you. If going dark is a cheeseless tunnel, I don't know what to tell you, but it will be harder for you to detach.
If she feels trapped, give her tons of space. Moving away might help. You might tell her that you are giving her space, and won't call her, but she could call you. I don't know. That might be terrible advice, putting you squarely in the spineless friend zone.
But just like you noticed, one good night's sleep can make all the difference. Whatever you do, you don't need to rush into it. You didn't get to this point overnight, and nothing you do RIGHT NOW will change it.
M:23 T:26 Me:53, Wife: 60 S:18 D:16 filed 7/16 W moved out 4/28/17