Does he really try so hard if he keeps replying to Tinder chicks?
It's not a big deal, if it's such a big deal to him then clearly his priorities aren't in the same kind of order as they are for you. It has nothing to do with Autism or whatever. He just has a different set of values, plenty of people think it's ok to keep cavorting around with exes and failed romantic options. Not only that, they feel like it's their basic human right to do so and that if you don't like that then you are a crazy jealous psycho.
The only reason you are angry is because you think that if only he just fixed this one issue it would've worked out and he couldn't even bother to do that. But in fact, this simply reveals a great big incompatibility in your personalities. It's seemingly small, but it's actually very big, there is a fundamental difference in the way the 2 of you think and this cannot be resolved by just fixing a single symptom. This is why he believes he is right and why you believe you are right and neither of you can give any ground. If it's not this then the next time it'll be something else you won't be able to agree on, because... you are incompatible.