Welcome to our forum.
Sounds like you may be in a bit of a state of confusion concerning what you want at this point. Is polyamory something you want, and is it a dealbreaker for you?
The other question is, do you want to try to save your marriage? If not, then you need to set goals that will make it possible to divorce and then pursue those goals. But I can't tell if that's for sure what you'd want.
Sure your wife has said "no" about poly one time, but it's possible she could change her mind in the future. Can your marriage be fixed? What would you need in order to feel like it had been fixed? What parts of it are broken?
Do you and your wife get along? Could you separate amicably? What would need to happen so you could get a car and have a place of your own to go?
It seems to me that you are facing many challenges, and the thing to do is pick out just one challenge at a time and work on that. Otherwise, it may all get overwhelming, and leave you floundering.
I hope this site is of some help.
Love means never having to say, "Put down that meat cleaver!"