I would not continue to let him live with you unless he attends counseling with you. He has REAL problems with his family's boundaries. If he doesn't learn to stop letting his mother intrude all the time with these calls, you two will end up divorcing one day. Why he doesn't turn off his cell phone when he is in the middle of visiting someone, I do not understand. And neither should you.
He shouldn't be discussing his financial situation with his parents. If his ex sweet talks them into giving her money, that is their fault and their son has warned them.
More than anything, I think that what very well may happen later on is that she will use them and then they will come to their son in need and expect him to financially support them. Because he cannot say no, and they don't have trouble butting into his life with both barrels, this is a train wreck waiting to happen.
You see all the warning signs. You're trying to put up roadblocks. I really don't think you are going to be successful. If he doesn't really see the light during counseling and decide HIMSELF that he is done with this stuff and put his foot down, then you should ask him him to leave and sever your relationship.