Married man for 20 years cheats repeatedly

I found out a man Id been seeing for over a year is married. Told me he's separated "done and dusted" was the phrase. Doesn't take me long to find people online. Not gonna say how I found out, cos F*** him and I don't want him to know but it was an easy Internet search. Turns out he's done it loads even when she was pregnant with their first baby. His wife is a stupid c***. She said she was told by other women it was just sex, but for us... he met some of my family, we had nights out, I had things in his flat like toothbrush, exorcise hour conditioner, bath robe. He'd put my favourite wine and snacks in his home fridge for me for after work for movie time. He's probably told her since I told her that it was just sex, but it wasn't. He invested time in me. I'm completely done so the time now seems like the biggest con, and I hope he jumps off a balcony. His sons don't need a mother who constantly allows a man to cheat on her, and they also don't deserve a father who disrespectfully cheats on their mother time and time again.