Everyone is basing it on the typical affair though, he doesn't slag her off, he constantly tells me how bad he feels for what he's doing and how she doesn't deserve it because she's so nice to him at home.
What is your source on a typical affair? Just because he doesn't talk trash about her doesn't mean he isn't typical. My guy didn't talk trash about his wife either. He just used to tell me about how they've grown apart & he thinks it is because they came from such different backgrounds.
Plus I would deserve it if he cheated
This right here is what you need to analyze. Consider why you think you would deserve to be treated in such a way. You clearly haven't forgiven yourself for past mistakes & don't love yourself enough to seek out true happiness. No one deserves to be treated poorly & you need to love yourself enough to believe you can do better than this.
but he's on home detox now, so the alcohol issue is being resolved.
Not unless he is seeking counseling to address the underlying issues of the drinking. Drinking is the symptom, not the problem.
It is possible to make someone happy so they won't cheat or be unhappy with their partner!
No dear, it isn't. You can't make someone happy if they aren't happy with themselves.