Well...
You have a lot going on...
I think firstly, what you want with a poly relationship is possible. Hell, your online!!Check out some dating websites that specialise in that. Also, not sure what kind of fetishes you are referring to, but I'm sure there will be someone- or people keen to try.

I hear a lot of emotion, but it's kinda rambling rants ATM. It would probably prove more helpful to be specific in what feedback you actually want, cos tbh there is far too much to desipher how to help.

You don't have to want to get married, but maybe the girls your interested in want a commitment, or at least to feel secure, that you won't bounce after getting some. Esp, if you want a permenent threesome. Though I think your overestimating how great that would be. Three personalities? Hell two in a relationship is more than enough. Trust me - I know...

Anyway, hope things get better.