I can understand your worries, but there is not much you can or should do with legal problems between your XH and his looney STBXW. If he is broke, I dont see how they can get him to pay for anything.

If he has told you that he would terminate his STBXW and then himself, it is possible that he has used the same line towards her and could be setting himself up for some jail time. Do you think he is bluffing out of frustration?