Opinions please

This is a really difficult decision for me so I need some outside honest opinions.

I've been with my fiance for about 2 years now. He's the only man my 3 year old has ever known and they have a good relationship, but..he has a drinking problem, like it's caused pancreatitis that almost killed him (before he met me).

He's always promised on and off to stop but never follows through. Lately have had a huge disconnect with him. Not turned on or interested in him in anyway so I told him I want to hold off on the wedding and now he's back to drinking every night again.

What's hard for me is if I leave I'll have to move back to the bad part of town to be able to afford a place, my son will have to go to a shitty school, and I'll be back to busting my ass all day by myself. Plus what if it's hard on my son emotionally? I feel like it might be traumatic for him.