One thing that gets me about AI chat agents is the idea of attack surface. If you have a clearly defined protocol you can curtail most of the possible attacks by narrowing things, only accepting well formed requests, and validating both on the user end and then on the server end before processing anything. An LLM is inherently wide in attack surface given the way it is structured. It can take a prompt which can be any set of characters connected together into tokens. These tokens can't easily be filtered for intent or goal and yet they can get the LLM to drop other rules or restrictions because they are just other prompts.
A simple coded padlock is not very secure, but a door with no walls is less secure.
Nobody is actually shitty here but some things seem like they are not going to work long term. It is reasonable to have a need for some quiet time and to unwind from work. It is reasonable to need connection and validation of the relationship. It is reasonable to be upset.
He is not being reasonable about how he interacts with you. He is taking your lack of ability to be social at the level he needs as a rejection of him and in turn rejecting you. This is a lashing out response and it is not appropriate or effective. It will either result in the dissolution of the relationship or it will result in longer term toxic behaviours which will then result in the relationship falling apart.
You need to work a little less. That is basically the conclusion you have come to above and that may take time to enact, but it needs to happen. Neither of you will be happy until then. So your action should probably be to reduce just as you have said.
On your partner's end he needs to build his own supports to take some of the load off you. He has a lot of free time that he could use going to a rock climbing class or something similar. That would give him the social interaction he cannot get from you at the moment. He also needs to work on how he talks to you about needs and his responses. He can't put his self worth entirely in your hands. It is unsafe for his wellbeing and horribly damaging to your relationship. He needs to internally validate his worth and that is a skill, not a trait, he can learn that.
Some of what you describe above sounds like he doesn't really understand ASD/ADHD very well and doesn't get how burnout works. Maybe he could spend some time learning about how to be safe and healthy for himself in a relationship with someone on the spectrum? It is hard to know how he would react to hearing this, but he needs to recognise that a relationship with you is not the same as a relationship with a neurotypical and he needs to take care of himself to be safe in that relationship. It is not worse, but it is different. If he doesn't learn how to manage his needs then they will continue to be unfulfilled and he will have a bad time.
And honestly, the dog situation is just devastating. If my partner lost their companion animal I would expect up to 6 months of very low function. For you to be working in this condition may suggest you are not able to grieve properly and are working to be away from demands, but it could also be it just doesn't affect you in the same way it would affect my partner, we are all different. Take care of yourself and grieve as you need to, maybe spend some time talking to him about it if you feel safe doing so.
Oh, and consider planning out movie night or similar things, make it explicit what you need and book it in. Those expectations in advance can help.
So yeah, NTA, but also, nobody is fully shitty here, his behaviour seems less ideal, both of you can do things to make life better, I think this is salvageable.