I might have some unique insight. I'm a ptsd sufferer from extreme childhood abuse. I'm also a published military author, though I've never been in the military. Writing about war has been therapeutic for me. One of my books is a memoir of a soldier from WW2. I got to know many WW2 vets through interviews. They became my friends.
Typically the contact would start like this and would take months to get any useful info. First they would say, "I don't remember". Later (weeks) it would be, "I just don't remember". It would progress to, "OK, here is something for you". They would say something unrelated to combat, but something funny that happened to them non combat related. Eventually, it would after many more weeks, "I fired at a tank. I fired at a enemy position." Eventually it would get to, "I killed....", The progression was the same in every case. There was only one soldier I couldn't get to eventually share.
When the book came out, the soldiers bought a lot of books to give to their relatives and friends. I got to know a number of family members. Basically what they did was say, here is a book. They hoped it would be read. For the soldiers, they told me that is was their way of presenting their story to family they had never told much about other than maybe the first couple of steps I went through. These guys were in their 80s and 90s. It was like popping a big festered pimple for them. Hurt like hell, but it provided relief. The family members mostly said, "I had no idea.."
Some family painfully asked me why they talked to me and not them. A few were really angry about it. Not that the soldiers shared their story, but that they shared it with me.
I would suggest just giving him a note or simply say that you watched it and say, thanks for sharing that. Maybe "I'm sorry you went through that". I would say you understand as it's just like those of us with non combat ptsd, no one can really understand.
My two cents.