You sound pretty anxious and bothered by his behavior so I think he is pulling away from that. And seeing one another every 2 weeks is ridiculous and he knows it and deep inside you know it too. It’s not sustainable for a human relationship.
You’ve known one another for a year and early on he was accommodating your NT needs. But now he needs more space for himself and he’s loosened up a bit and maybe is more himself, except now you are showing extreme discontent and confusion with how he is.
He isn’t emailing back because he’s hesitating, wondering if it’s even worth the effort at this point, he’s doubting that he can truly make you happy. For the past year he’s been pulling a circus act for you and he simply can’t sustain it, he’a probably lost a lot of himself in the process.
The 2 week “arrangement” screams you have a syndrome, a disability and this is how I will accommodate you. It doesn’t express love or acceptance. It says, get some rest then after 2 weeks go back to your circus act so I can be happy with you again.
You need to get to know him better and let him know you appreciate him and really accept him as he is. If you can do that I’m sure he’d be happy to see you everyday. An aspie wants a normal relationship afterall, not a weird one.
One tip about email and texting... from my perspective as an aspie, I hate emails and texting when it is an extension of small talk. You are entitled to check in with him as you please, but if all you say is “hi”, he will not know what you want him to say and will have to make up some NT thing. I have NT friends who could banter on and on by text/email and I am truly amazed even impressed with how natural and easy they make it look. I love that they build rapport this way and can play with words like they do but I never participate. My mind is too literal and I spend a lot of time in my head. Often times the words I think about are best put in an essay and I haven’t a clue when it comes to banter.
That said, most NT’s require this kind of engagement to feel connected whereas aspies do not. You may have to ask yourself if you are ok with this. If you are, then the next time he doesn’t respond to your email or text simply ignore it and realize it doesn’t mean anything. You could also mix it up and try being a little aspie yourself I.e. instead of “I miss you, I want to see you, what are you doing xox blah blah blah”, just say “going to a movie, wanna come?”
I think if you loosen up, act happier and less insecure, he’ll be more inspired and have the energy to be with you.