I always find that it is helpful to have straight forward questions and answers. It might help to ask him specifically what you can do to help him and possibly better/ deepen your relationship. I know my biggest things for me are not lying/ being straight forward about stuff, telling me about any changes that will happen in our schedule (my fiance has two kids so this is a big deal), supporting me (which is normal) and also letting me have time to myself to recharge/ stim if need be. Also, if he tells you that he needs to leave somewhere (a party, for example) then listen to him and get him out as quickly as possible. Of course, it is only fair that he tries to be supportive of you too. You asked about how you can help him, so I just stuck with that.
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--Nyx-- What an astonishing thing a book is. Across the millennia, an author is speaking clearly and silently inside your head, directly to you... Carl Sagan