Aside from his from character (he fucks around with another woman and tries to jump ship, having married and created a family with someone, tries to blame them, rewrite history etc.) .....
I would see any reconciliation as very tenuous, and therefore unwise because;.
A ow's husband is in shock, preservation mode, possibly hysterical bonding etc. He, like many spouse's, may think ge can forgive it, may try to forgive it . . But may not be able to. If he leaves, she's available and for more likely to entertain your husband again. Do you think he'll stay, given How's he's acted, what's he said, and what he saying now? He's told you he despises you, he was seemingly prepared to leave you, he's only said said wants yo make it work for your son, now he's saying he's committed; bit ues not said he was wrong/lying about despising you, or wrong/lying about never having been happy (or not being happy for a long time). He may say it if you demand it , but would be be truthful?
His plan a has tanked, he doesnt want to be a single/separated man living in his parents house, looking like a loser, looking not respectable etc. Thats appears most likely.
B OW could change tack and leave after all. Same implications as above.
C OW abd your dh could go back to being involved when danger/crisis etc is past. That happens. Same implications as above.
It's a city tenuous socialism you'd he putting yourself in, depending on the whims of OW, ow's husband, and your husband. I worry you'll come out the victim again.