Couldn’t read and run OP.
I have Crohn’s disease, and what your son is experiencing sounds very like it. Obviously I’m not a medical expert, but I have experienced a lot of the same.
You need to insist on a scope. They aren’t pleasant, but you may find a surgeon who will do it under general anaesthetic if your son would be more comfortable with it. I had to swap hospitals to get a surgeon to do it under GA, was too painful for me to do it with Just sedation, tried a few times.
The only way they can diagnose Crohn’s is through a scope. CRP etc can only indicate that it is a possibility. They need to take samples and physically see inside to get a proper diagnosis.
I feel for him, those issues he’s having are horrible. IBD is a bitch to get a diagnosis for, they’ll try and rule everything else out first.
Can you get him to an out of hours doc? Ime, out of hours docs refer you for the scope quicker. If he’s bad at the time, they could even admit him and do it within a few days. That’s what happened with me 7 years ago and what is currently happening with my sister, unfortunately. She is like your son, they have said it’s ibs etc only when she went to out of hours did she get referred for a scope.
I hope he is more comfortable soon, sending best wishes to him