If Jer didn’t become a fat alcoholic retard without personality, maybe the marriage would have been fine
No, the marriage ended when she fucked someone besides her husband. His mistake was forgiving her and allowing her to stay (and apparently continue fucking other men). She should have shown him the basic decency to divorce him first before climbing back aboard the cock carousel.
No self-respecting man (I know, that rules Jer out immediately) tolerates infidelity of any kind, even once. That's literally the first fucking vow you make at the wedding ceremony ... that whole "forsaking all others" bit. Violate that and nothing else you say or do ever matters. You've destroyed the marriage, betrayed your spouse, and revealed yourself to be a whore. It's not "a mistake." It's not "an accident." He didn't "make her do it." She exposed herself, spread her legs and let another man in. It was her conscious choice. Even if the other man was very aggressive and applied a lot of pressure, she still said "yes."
The moment he first found out she'd done it he should have kicked her to the curb. The fact that he didn't proved to her she was free to do it as much as she likes, because even if he gets upset later on, she can always claim "hey, you were okay with this before! That's not fair to change your mind now!"
Fun fact: that "gracious forgiveness" will fuck him again when the divorce finally does happen. The longer you're married, the more likely the court will be to award your whore ex-wife alimony anyway despite her infidelity (and yes, your tolerance of the behavior contributes to that decision). In some places (lookin' at you, Florida), at the seven year mark there's a practically-automatic "alimony for life" awarded to whichever spouse earned less at the date of filing (and the receiving ex-spouse has to fuck up
hard for the paying side to have any chance of wriggling out of it), and what's worse, infidelity doesn't mitigate it either (thanks, "no-fault divorce", stupid fucking feminists).
Don't get me wrong, he's a fucking asshole who deserves all this and more. It's just that as a man I hate to see it happen to an other man as a matter of general principle.