My son... UC

[Gabriel]

I've had MC for 10 years, quite under control with GF and SF diet.
My son, 44, has had a colonoscopy that revealed UC, asymptomatic for now. He's on Mesalamine.
He did the Enterolab test, which returned rather disheartening results:
Anti-gliadin=48. Anti-casein=33. Anti-ovalbumin=54. Anti-soy=28. Mean value of 11 antigenic foods=20.
Of the 11: Walnut, Cashew=1+; Corn, Rice, Tuna, Beef, Pork, Almond=2+; Oat, chicken, white potato=3+.
One doesn't quite know where to begin.
I have the following questions:
(1) What is the likelihood of asymptomatic UC turning symptomatic?
(2) Can one stay indefinitely on Mesalamine?
(3) How does one begin to design a diet with so many immune-stimulating foods? Is it reasonable to drop so many types of food cold turkey?
(4) I have two granddaughters, 10 and 14. Does it make sense to do the Enterolab test at their age, and if not, what is the right age to do it? In other words, do these reactions start in childhood or develop only later?
Thank you so much... It was this forum that helped me bring my MC under control.