You could as an alternative wait for the month to find out if he's going to come back or take on a new lease

If it looks like he's going to keep down there, then I would reccomen you use this approach...

If he may come BACK because he's broke, I would use

EXPOSE
CONFRONTATION

in that order.. I assume you have told most of your friends and relatives he's having an affair already anyhow, so expose phase is already done.

BUt I wuld NOT invite him back into your home until the confrontation was done and he agreed to end his affair.

It really all depends on how things turn out down tehre... assuming you want to use his shaky finances as leverage to provoke him to return there.