You and H have been separated for about six months, right? So my opinion is the same as yours. It's time to let his family know. This shows no signs of ending soon and it's unfair of H to expect you to keep doing this.
Too bad if he doesn't like it. He's done alot of things you don't like, too. I think it's time.
It's really hard not to focus on H when you love him. But keep trying because you can't fix him and you can't control him. The only one you can fix and control is you. You are obviously totally stressed out if D is noticing and being upset by it.
Hard situation! I got really really tired of being upbeat and comforting and keeping my mouth shut all the time so he could spend time and nights with OW. That's the hardest part to me. Sooner or later you can't do it anymore. No matter what the consequences are. Good luck in whatever you do!
