I'm sorry to hear about your S and how hard he is taking things. My e and I split when our D was 6 months old, so she never knew anything otherwise. Ex married OW, they have been married 5 years. For some reason, even though my D7 at the time never knew anything other than us being divorced, she was having a hard time, hating splitting time between the homes, didn't understand why she was with me more than him and since she never experienced the divorce, or saw unhappiness, she couldn't comprehend why we weren't together. I took her to a therapist, but we couldn't really find one locally, so I spoke to the school guidance counselor and she started seeing her once a week. Then the school developed a program where some peers in her grade come from divorced families sit down and talk to eachother once a week. It helped her greatly. She felt like she wasn't alone and she had an outlet. My daughter is every therapists dream, she will talk about her feelings all day long, you don't have to yank anything out of her, lol. I know it could be different for boys. Maybe ask your S10 if he'd like to talk to a therapist. Sometimes they need an outlet that isn't their parents so they don't worry about what they might say. You spoke to him perfectly, you handled it great. He just might need an outlet.
As far as your ex becoming chatty, I don't like to assume, but it probably has to do with new guy. My ex who isn't typically helpful, but we get along after all these years, offered me, D8, my new guy, and his D6 a ride home from the airport during bad weather. We had a crazy day, missing flights and getting delayed, and wanted updates the whole way to make sure everything is ok. I texted him saying we got uber, we were 20 minutes away from home, yet he still wanted a text when we got home. he never cared before, even when his D was involved, all of a sudden he was caring.
You can chose to be chatty back, or not, when my ex is rather friendly, I go along with it. When he isn't, I ignore him.
Post D R's with ex's can be very strange, I just learned ot take them in stride.
