I have not fully read your sitch ... but ^^^^^ all screams MLC to me, I am probably towards the back end from the signs and let me tell you , its been a rough 4-5 years. Thing is the logic, what guy at 45 would want to start all over again, and lets just say for the sake of argument this is what he needs ... we are not talking a puppy here, is he really going to go to a HS graduation for his son at 64? ... WOW Other thing is .. ok, you really feel you have to have a child and be a FT parent, adoption is an alternative.
My wife did similar, she wanted more kids, we started late, had a miscarriage then turned around and had S, tough pregnancy and an emergency C section ... yet she still wants more kids but was blaming me for the fact she felt she could not have them.
All you can really do, just as DB'rs in common situations do, validate, he knows you do not want a D, but you also have to make sure he knows that once the D is final so is the friendship, they must feel the loss somewhere .... inbetween all the fantasy thoughts about how life will be so wonderful because its only the M that is holding them back ... *rollseyes*
I will see if I can catch up on your sitch but yeah .. sounds like a bit of a MLC thing on the surface.