I get the impression you don't see yourself as this guy's equal. Guys generally pick up on this, and some guys might even take advantage of the situation. It's not a good way to start a relationship.
There really are guys out there who would be thrilled to date you. Autism shouldn't stop you from having a good relationship, because autistic guys are in the same situation you are. Many autistic guy would much prefer to be in a relationship with someone who thinks like they do.
You really shouldn't worry about your weight either. The beauty magazines lie, curves are good. Some guys only go for bigger girls.
It's ok if you don't appeal to everybody, you don't need to date everybody.
Forget about this guy. See if there's a meetup group in your area for people with autism. I know single ladies are in short supply in my local group, I suspect you'll have more than one nice guy looking your way.