I agree that engaging with the Disability Support Office is incredibly important. (It may have different names at different universities.) They are the ones who arrange for the taking of exams in quiet rooms, extra time, and other accommodations to meet students’ needs.
Often ND students feel that university is a fresh start and they want to leave their autism behind. Either as part of this, or picking up on what other students say, they decline help on the grounds that they don’t want special advantages. But as I tell my ND personal tutees (when they bring their autism into a conversation about academic difficulties), the options being offered to them aren’t designed to give advantages, they are designed to level the playing field. If you decline them you are actively disadvantaging yourself. Why would you do that?
The clods grumbling about ‘unfair advantages’ are usually such competitive types that I can persuade my ND tutees they are just jealous.
The DSO is also just a great resource full of nice people. If your DS ever submits a Mitigating Circumstances petition - and as a long time panel member I have the impression that at some point most autistic students do - he might be interested to know that at my uni and others, someone from the DSO attends each meeting. Working with the DSO is an important piece of evidence that you are attempting to manage your health condition; furthermore, the DSO person makes sure their students are being treated well by the Schools. Registration is kept quiet and shared only on a need to know basis.
The other thing is that autism is much less of a barrier than it used to be and your DS can find his people thru hobbies, volunteering, etc. But he will need to be proactive. Making a fairly explicit plan with him ahead of time could be important. I also agree Uni is likely to be more full on than he can imagine, so a living situation that provides some privacy at the end of the day sounds important to me.