@Aeris, welcome. I am one of the "old married guys" here on the forum. I am 56 and have been with my wife for 37 of those years. Yes, I was 19 when we married. Having said that, I was not diagnosed until I was 52.
In my experience, the vast majority of relationship troubles are due to communication issues, even with neurotypicals, but especially with those on the spectrum. Many of us have some degree of "mind blindness" where we have little idea of another's thoughts, feelings, and perspectives. From that context, this often demands that a different type of communication style be employed when dealing with the autistic individual. One, both people have to be acutely aware of this "mind blindness", so this translates into being accurate with your language with each other, and using "direct" language not "indirect" language. Neither of you can "assume" or that "he/she should know" anything. No hints, no working up to a conclusion from asking questions, get to the point. Heterosexual males, right or wrong, are often conditioned to suppress their feelings. They internalize. Furthermore, if a male does express emotions to his partner, the female gets upset and everything blows up in his face. So he learns from that and wants to avoid those emotional conversations. Furthermore, still, a high percentage of autistics also have alexithymia where there is a brain-body disconnect or processing delay where we might not be able to identify how we are feeling "in the moment". If someone asked me right now how or what I was feeling, I would say,
"Absolutely nothing."
In my experience, my wife and I have learned to embrace "quiet time", whether it be at home, in the car, out on a date, whatever. I am mentally incapable of "small talk", so when we do interact it is about specific things like the kids, the house, the finances, work, etc. We get straight to the point and then we are done. When we do spend time with each other, for the most part, we don't need to talk, but simply being there is often enough.
Meltdowns and shutdowns are most often due to a build up of stress and anxiety, and this is more like over a prolonged period. The pressure builds and then some seemingly innocuous trigger will be enough to cause a rather embarrassing, but violent outburst of emotion. Keep in mind, if he is an internalizer, then what you may notice is the "shutdown" first, the avoidance behavior, and then if you push him just a bit, then the "meltdown". Obviously, whatever is going on in his life has got him into this "shutdown" mode. Work life, especially if working with people, can mentally exhaust anyone. Quality sleep helps significantly, and I am guessing by now, he probably is either mentally wiped out or is already taking afternoon naps. Avoid sugars/carbs. Don't even buy them. Seriously, sugar raises havoc in everyone's brain, but especially autistic brains which are already under physiological stress. The insulin spike can vasodilate the cerebral vascular bed causing a low-grade cerebral edema. It's not a headache, per se, although it can be, but more of an internal pressure within the skull and you feel like crap, and if you have sensory issues, it exacerbates them quite a bit. So, a lifestyle change may be in order. Dietary supplements like melatonin, resveratrol, chelated magnesium, methyl-B12, and probiotics, etc will help. Restrict the caffeine. Restrict the carb intake in place of more good fats, salads, lean protein sources. Go for walks outside, fresh air and sunshine and a walk around the block can do wonders for the mood and relaxation. Intermittent fasting is great for the brain function, as well.
Well, I hope I gave you some ideas.
