Sometimes DSA will give students their own academic skills mentor and a mental health mentor (someone to just talk to about wider life stuff and stress. Does he have either or both of these? He looks like he should qualify.
Has he been referred for therapy by the GP? Or could he access it via university, these tend to only be 6 weeks though, but ask disability services as they may have one with more sessions for certain students.
Does he have an LSP? They should have sent him via uni email a copy of the LSP. They will also explain all staff to him and their roles, ask library staff to do an induction, allow him extra time and other exam arrangements of his own room etc, being able to record lectures etc. Also things like not asking questions on the spot, arrangements for things like coursework, presentations. Make sure it includes all of this.
Disabiltiy Services are very good with this adding exam arrangements (extra time, rest breaks, scribe, separate room - ask for all the possible exam arrangements, as universities have lower thresholds), tools so recording lectures, and your dc should also have get some assistive technology from DSA which can help. Has he gotten his DSA2 letter and the equipment yet?
Your DC needs to go to office hours, and have sessions with his academic tutor (great that he went with you, hopefully that means he'll go by himself again). What progress or steps etc were made in that meeting?
Talk to his lectures and his Disability Advisor regularly. It's good you are involved for now, as he gets on and hopefully is enjoying it, works with support services etc, hopefully he can mange more himself which can be good as he gets towards the end of uni, but obviously not a concern for now.
Could he join any sports clubs? Something that's sort of more yes sociable but also your focused while doing it? Glad he's started going to a few lectures