Unless he already has lots of friends, he might also benefit from having a male friend in the family who knows about the problem, who is on his side in all this, and who will listen without being judgmental.
Just listening while he vents and thinks out loud would be a huge benefit for him. Well, assuming that gambling SIL would allow it.
He was being sued in a business related matter and we successfully settled this afternoon so I invited him back to my house for a little celebration and debriefing. The gambling wife is a much bigger issue and stressor in his life than this lawsuit though.
W2R, what you described above, the listener, is basically the role I played today back at my house. And it is what I have done multiple times in the past for him. Just listened. Let him say what's on his mind and work through his thoughts.
After listening for quite a while, I offered him help with financial issues today (from a money management standpoint and a legal standpoint). Then suggested if he is interested in a divorce attorney I could get him a name. He's not ready to do that yet. We talked about finances a little and he doesn't really know how much debt the SIL has on credit cards. She has been using BIL's credit cards some too, and the balances are higher now. I think SIL takes care of the bills in his household, so he remains relatively uninformed. He has just taken all his credit cards back from her and keeps them away from her now.
BIL has been trying to sit down with his DW and get all the debts (CC, gambling, family debt to MIL, etc) all out in the open, write it all down and figure out what they have and what they owe. SIL has refused simply stating "You know how much debt we have". BIL clearly doesn't. At least not the full picture.
I asked BIL if he thought they would have anything left if they tried to pay off all their debts and he said no, probably not. He said he's at the point where even if he got out of the marriage now, there wouldn't really be anything to leave with besides debt. I guess he figures the worst case is eventually splitting up, filing bankruptcy and starting from scratch.
We also discussed the possibility that his DW may be manic depressive (he brought this concern up, though not using the clinical term "manic depressive"). He says it is definitely possible. She gets very excited Saturday when it is time to gamble and Monday when the gambling is over, she mopes around the house in a depressed state until Saturday. She's too stubborn to seek treatment, but at least I told BIL that all it may take is taking a pill to at least partially "fix" her.
I think BIL is informed as to his alternatives. He understands that he's probably going to end up with nothing financially regardless of whether he divorces now or later. He thinks his DW may hit bottom when she realizes there is no money to pay for the house, utilities, food etc and all the credit cards are maxed, and no one in her family trusts her (this latter event has already occurred). They aren't too far away it sounds like.
BIL did say that SIL is upset by losing the status as caretaker of her parents' finances. She now sees that her gambling and horrible financial management of her own money has caused other people to not trust her. But she still hasn't accepted that she is the one responsible for this.