You know, I wouldn't tell him you know about the phone call - only because you want to be able to continue to monitor what is going on.
On the bright side, though, you don't know what the content of that call was - could have been a long break-up call.
What I recommend is that you focus on YOUR life. Focus on having fun, trying new exciting things, making plans for your future, getting financial ducks in a row in case he ends up leaving. A guy like this is depressed about aging, looking for excitement and something "different" thinking it will relieve his depression. The best thing I got out of my whole DB experience was that it kicked me out of the mode where I was just trying to take care of everybody else, into the mode of thinking about what I really wanted out of MY life.
I thought that I was doing the right thing for my marriage by compromising and placating my ex, but in reality, I think we would have fared better if I had stood up to him more. I think he lost some respect for me because of it.
When my ex finally left, I bought a drum set and learned to play the drums - at 53. The kids thought I had lost my mind, but now I play in a punk rock cover band. My youngest son just came out to a gig of ours last week and tole me I totally rock!
Try to take some of the focus off of your H and put it into renewal and growth for YOU. Regardless of the outcome, you'll be glad you did.
