Orlanda, your poor DS.
Does he know why its so tough. DD expected it because medicine usually is, but DS (economics and a 4A* prediction) did not. He ended up with the offer he wanted, and you only need one, but looking back he says his PS really was not good enough.
If he has an idea, and he should ask for feedback, he will be better able to reapply, making sure his application is stronger (do more reading round, relevent work experience, have experienced people read over the PS, etc) and pitching at the right level of institution.
He needs to get working now. (I am sure you have told him that!) The better the grades the more doors that are open, plus he has more chances with clearing. For competitive courses I think it helps to have actual rather than predicted grades. Certainly decisions seem to be quicker.
I get the mates thing. DS was quite upset when someone else got an offer from a course/University that had rejected him. The poor boy then failed to get the grades. Its the old thing of life being unfair, and sometimes you win and sometimes you lose. DC who have had a smooth passage through the UCAS process, presumably will have to learn this at a later stage. DS in contrast struggled to get a summer internship, but now knows you check that you are pitching things right and then keep on trying. He finally got one last week, so is in a better position than those who gave up after the first rejections.
So tell your DS not to worry about humiliation and start thinking about what he might do in a gap year. Having Plans B, C and D help when Plan A seems to be failing. One option might be this www.workaseason.com/ essentially November to after Easter. Apparently a good proportion will be reluctant gap yearers and they allow people, albeit at their own expense, to fly home for interviews, however there is quite a lot of demand so you need to apply around May/June. A good gap year, with new skills, ought to make him a better student when he finally gets to university.
Fingers crossed on the last one.