Very sorry to hear Natasha,
Sounds like the marriage is in deep Do-Do, Any Ultimatum is unhealthy for any relationship, it just makes it worse & causes bitterness, and a councillor may be needed to help both of you figure out how to improve the relationship if it's possible, and it sounds like there's more to it than just the dressing, & she has other issues too.
If you two still cannot see eye to eye after that, then the inedible will follow with separation & divorce. or you both just live in misery, but that would hurt the children more than any big D will.
Sounds like you need to do lots of thinking & have some tough decisions on your future.
Good Luck & God Bless
Karen