welcome. I am in the process of a divorce from a marriage as long and arduous as yours. For me the hardest thing is being lonely. Having someone to call, to go out with, to watch TV with is something that I crave. I am not dating as I am not actually divorced - and I don't trust my taste in men. In fact the ones that I think are cute have a lot in common with my stbx, and I think it can take us a lot of time and conscious attention to become attracted to healthy after so many years in bad. Bad just feels comfortable, like you said.
Do you have children? They are a good motivator for not "adopting" a dysfunctional boyfriend.
read and post - it gets clearer and better.