Is being true to his promise such a great thing? He is totally being taken advantage of and quite frankly is being abused. If he was doing that to his wife he would probably be brought up on charges. He needs to establish some balance.
I’m not sure why he subjects himself to the threat of being shamed as his reason to put up with her behavior but perhaps the fact that he does put up with her is why she calls him names. I would consider removing all traces of DL interests so he can disavow it (unless there are pictures or other evidence) and then have a reset of the relationship. No reset, then threaten a separation.