Alarming is right...the cheating/honesty issues got triggered big time.
After he moved in ...way too fucking late to have good options or good conversation.
Does she see a positive (big , small ...any) for you?
Devils advocate here....how about asking if she'd be ok with you being the secondary just to see the reaction. To me it's more of cake eating position....lets somebody else buy the ring.. have the responsibility, the day to day operations....85-95% of the time float in for the fun. Track her periods and ditch those days for sure.
Dart night ...book club...bowling league whatever.