Oh yeah, that's right. My apologies. I knew it was one of them places and that England didn't feel quite right as I was typing it...
Irregardless.
I won't tell you what to do because I don't know the situation beyond what you've shared with us internet people, but I will say: Don't over-rationalize things if the situation continues to deteriorate; if it's bad, it's bad, and you deserve to be treated better. Don't hold on with the excuse of "well I've already invested so much time that it would be a waste to throw it all away" because you can only waste more time. Don't hold on with any excuses, really.
Work on becoming more financially independent if you can, and do try to get him some help if you believe he'll be receptive and willing because he really does need it, and I can tell you care a great deal for him, and if he cares for you then he'll be willing to make changes for the both of you and your relationship; but don't spend your life trying to change someone who isn't willing to change.
Matters of the heart are tough, especially when complexities are involved. I know them feels, bro.