Your current MH has taken a beating and your friend has tried to bat for you because at present, you can’t.
Hopefully, this mess will be the catalyst for you to move forward from your current marriage stalemate. The fact you could not see the peculiarity in your initial post, suggests that your ability to see the dysfunction in your marriage and the need to resolve it’s issues, is compromised.
I’m guessing if your H had a ‘gf’ without your knowledge then you haven’t discussed an open marriage. Did the gf know your H was married? If not, the dumping of his arse was more to do with the message (the deceit) than the messenger.
With your marriage in such a precarious position, I think the career break has to be put on hold. The next time your H finds a ‘gf’ might mean that he decides to end the marriage on his timetable, not yours.
Ignore your H’s moping but you cannot go on ignoring the probability that your marriage is over. Which I understand is very difficult to accept but if you don’t, the pretence will destroy what’s left of your self esteem.
Where do you see the future? You can’t get there without some sort of plan. It’s time to start making one.