All of those scenarios can only happen if the spouse intends to keep attempting to cheat. If it's obvious the husband has no remorse for having hit on me, then yes, of course the friend needs to be told. But that whole adage "once a cheater, always a cheater" is just not always true. Some people truly have a momentary lapse in judgment, and the realization that they've risked everything is enough to scare them shitless and they never try it again. I've seen multiple marriages survive adultery with no relapse, and the other spouse didn't always know about it.

Yes.. if they are propositioning me... they are probably propositioning others too... friend needs to know what is going on...

I'd want to know...

My "friends" didn't tell me about my ex... I wish they did... I'd have left sooner

The friend deserves to know. It is not for you to decide if that incident was inconsequential. It is between the friend and the spouse to work that out. If it was truly a momentary relapse, then let the spouse convince the friend of that. You do not have the right to make that choice for the friend. Just like you do not have the right to deny them the full honest truth.

For everyone involved, it is better to know immediately, even if it seems like it's so much worse at first.

I replied on the assumption that he meant it; and yeah, I'd start with telling my spouse, but tend to think that if a guy is trying it on somewhere, he'll be trying it on everywhere ...