Very sorry and understand your feelings.
So glad you trusted your instincts, they are spot on.
Stomach is the first place my DD feels egg and she will compare other stomach pain to it and say, this is "not like the egg pain". Only one other food caused a similar feeling, sesame, which she is highly allergic too.
Our story was that DD passed a baked challenge, 6 months later passed a direct egg challenge, and about 3 months later reacted to egg but weeks before began not wanting to eat any and complaining "eating egg hurt her stomach" (doctor poo poo'd that.....NEVER again!).
For her, she was never truly not allergic. In mother terms, I believe her body was able to process a small amount of egg until it decided enough was enough!
Today, at 16, she does tolerate baked egg but it must meet the full criteria of being mixed with wheat protein and baked at a high temp for longer than 10 minutes.
Has your son's system settled down yet from the reaction?