He does sound like an Asperger's type of person. Does that trouble him in other parts of his life? Friends, education, job? Him being in his room, doing his 'thing', whatever it is since you didn't mention it, it is likely a coping mechanism. A way to protect himself or to not have to deal with the outside words on their, not his, terms.

You talk about 'nagging', 'complaining', 'stressful' and other words. I always imagined I would one day have a GF that would enjoy the challenge of getting me engaged in things. Maybe this is a very unrealistic expectation of an Asperger-type person of a GF and this is not something you can provide. If this frustrates you to no end, you may have a very hard time long-term. Because it sounds like this is a personality trait he has and you will have to keep doing this, hopefully in a progressive way, as long as the relationship lasts to make sure he keeps improving and does not revert. That's how I imagine things, at least.

It is true. You can break up with him and find someone who does know how to naturally maintain a romantic relationship, keep it balanced and engaging from both sides.