So things were good until a year ago? He didn't communicate that he was feeling unhappy ? He just decided to become shitty? 

If you truly want to fix it, demand counseling. Let a professional evaluate both of your mental healths. 

Perhaps it's salvageable, or perhaps you two are better off apart. Objective professional help is the only way to salvage it, if that's what you want. If not, lawyer up and prepare for a rough ride. Wish you the best of luck.