That's good that you had that talk with him. It must be hard and confusing to him right now. He knows that you are there for him. Hopefully his dad will start spending more time with him, as it sounds like he needs that.
I'm pretty lucky in that S13 is handling this pretty well. Neither H nor I have discussed details with him - ie he doesn't know about OW and H and I have an agreement that any new partner to either of us (not planned on my part) will have no contact with S13 for at least 6 months from date that separation becomes permanent - but he's known for a while that something was wrong. He thinks that a lot of it has to do with H's PTSD and we're both leaving it at that for now.
I've explained that we both have to prepare to not have H back any time soon, if ever, and that the only thing either of us can do is be a family together that H wants to come back to. The kids in the neighbourhood that he spends a lot if time with have just gone through their parents' D so he's been able to talk to them a bit. I have suggested he not discuss it with their dad as he's best buddies with H and things might get back to H.
H was around all day yesterday - went to nearby amusement park for the day - and all three of us had a great day. It seems to help that S13 still sees us having fun as a family. It seems to reassure him that we are still working on things. He also seems to know that asking his dad to come home would not be a good idea right now.
Both 50 S14 M 16 yrs (his 3rd; my 1st)
ILYBINILWY - 24 Dec 2012 H moved out - 27 Jun 2013 Legally separated - 6 Sep 2013 Closing the door and changing the locks