Hi Terry! A lot of what you’re describing your son experiencing sounds like Autism to me. Anxiety can make a person more sensitive to sensory input, and can be draining, but it does all sound very familiar and resonant to me. I would recommend that you and him check out some of the Autism resources I linked to throughout my writing: Amythest Schaber’s Ask an Autistic Youtube series, the tumblr Neurowonderful, RealSocialSkills.org,etc.
You asked if there is any benefit to being diagnosed — as an adult, not really. It can give people immense piece of mind, but the process is lengthy, specialized, expensive, and can lead to a person receiving more stigma from their doctors and therapists afterward. I think self-diagnosing as Autistic (or on the spectrum) and then seeking out resources by and for Autistic people is a good idea for a lot of people — the Autistic Self Advocacy Network is a good place to start, but also local Autism meetup groups that the like can be good.