To be fair, while one would think that a 38yo man could protect himself, one would also think that a wife would not go telling his mommy about what he's done. Not only have you breached his privacy and criticised her child, but you brought her into the problem too. Now, that's not to say that what she's doing is OK, but I do wonder if perhaps none of this would have happened had you kept the issues in your marriage to yourself and not broken the rule about complaining about his family.
And for the record, it's not the done thing to criticise a spouse's family no matter how awful they are. It's OK if you agree with him when he complains, but it's not OK to make your own complaints. And of course, it goes both ways - he shouldn't be saying anything bad about your family either. This rule is pretty standard in all relationships.
All that being said, is your marriage worth saving? You say that it's not the best relationship and you have a hard time trusting him. So what's going on? Would you be better off out of there?
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.