Indeed his friends from school and Uni keep in touch with us too and are all of the same opinion.
Leaving aside that is not particularly common for significant numbers of school and university friends of a man in his 30s to have a direct relationship with his parents....all share your opinion ?
That is an unusually high percentage (unless we are talking about just 1 or 2 individuals, who perhaps your son felt were too far over the friend boundary and into a more direct relationship with his parent to include in his future once a rift took place)
If these friends are in contact in more significant numbers, it's unusual because humans tend not to be so uniform in such a wholesale fashion. There are almost always those with hidden life shadows of their own. Or possessing a more cynical nature. Or with a strong preference to not be seen as taking sides when it comes to other peoples' rifts. Just in case it makes things awkward when the central figures make up, and the earlier lining up on one side is now an elephant in the room.
Those sorts of people lean towards being disinclined to cast their hat into the ring by stating they are of the same opinion. Which tends to drag the rate below a flat out 100%.
It's not impossible, but from the perspective of an outsider, if I take your posts as a "whole truth, all the truth, nothing but the unvarnished truth" account there is a growing heap of probability outliers stacking up around you.
Those are not odds I would gamble my relationship with my son on. My position and advice, cos I really don't want you in this club for any longer than you need to be, remains the same. Focus inwards not out in your quest for answers as to why your son could possibly be willing and able to cut off a healthy, loving relationship with his parents.
Millions upon millions of DILs all over the land struggle to get on with their in laws (and vice versa) . For cultural and personality clash reasons. But their well bonded (in the child/parent sense) husbands stay attached to their mother and father and in their lives. Despite any ructions and upsets along the way. Why did your son not ?
Until you are able, with radical internal honesty (which incidentally sucks like a bastard, cos it is hard and painful) , to get somewhere close to HIS version of that missing answer, be you an outlier amoung outliers, or something more typical of the pattern, you risk staying in this limbo long term.
Potentially for all the time you have left. I know people say time heals. But what they often fail to mention is that is also runs out. It goes faster than we anticipate. Days bleed into weeks, into months until you look up one day and notice the years have become decades. At the nine month mark you still have time to wheel this around. It hasn't become an engrained habit of being yet. It's still too soon for the rift to have solidified into a "better the devil you know" status while reconciliation has morphed into the distant, unknown alternative that is too scary for you to even contemplate.
You still have time, but not so much left that you can afford to waste it on well travelled ground, that has got you nowhere,
I repeat. I am the last person who wants you in this sad, broken hearted club. I am stuck in it forever because dead people don't rise. But you, in your far worse position of yearning for your missing child, don't have to be.
And as horrible and unfair as analysing the situation with a brand, new lens may feel, it sure as hell beats the alternative of going around and around in circles over the same old ground, until time runs out.