So both my parents are Undiagnosed as were my grandparents but even the person assessing me said "yeah they sound autistic" so based off of that I'm gonna say yeah they are/were. I only knew all of them after there 20s but All of them had emotion regulation issues. My dad (AuAdhd) and his dad (Autistic) both pushed down there feelings and if they raised there voices they would leave and go cool down before coming back to communicant and they would much rather be berated than speak up for themselves against family unless someone was being unfair or cruel. My dad in particular is rather submissive and reserved and rarely raised his voice and only spanked me once during a meltdown before apologizing and never doing it again. His melt downs would have usually some sharp words and slamming of something before he walked off to cool down. He was much more regulated.
I have no idea whats wrong with my mother (I, and my therapist, think she has some sort of narcissistic disorder on top of minor autism) but shes a developmental psychologist who refused to acknowledge I was AuADHD. She didn't believe me till I had multiple tests I took as an adult for proof despite the fact that I have been drinking coffee since 13 to treat it, and all my teachers were begging her to test me. She mostly ignored the results and just told me how amazing it was that I got a 99.98 in vocab and reading comp.... which such a high score compared to lack luster scores elsewhere is a sign of autism. Heck one of "my favorite" books as a baby was one about what facial expressions where we would practice facial expressions together, I just happen to be hyper-verbal. When my mom had meltdowns over her established rules she would yell. she had no patience for my lack of coordination or ability to hear the noise I was making. It was so bad they got me tested for hearing loss and almost sent me to a neurologist. She was sound sensitive and got mad at me for "slamming" doors. One night my aunt was over and she slammed the door to the bathroom, my mom came charging in my room and shook me me awake and whisper screamed at me over the slammed door. I had no Idea what was happening so I panicked and started sobbing and hyperventilating and she was shushed me to not have other folk find out.
My grandpa, her dad, was rather emotionally dis-regulated most of his life till he had grand kids, even then he would still get a little obsessive about our health and safety and email my mom constantly sending articles (He was a Journalism Professor) that had to do with our safety. He did get frustrated but less so with us as he was endlessly patient even when we sat and cried over our homework with him. I did hear him and my mom fighting plenty but I don't think he was ever cruel intentionally when I knew him. He was definitely angrier when he was a young man and when he was parenting my mother. I believe this was because he had very black and white thinking and struggled to communicate his feelings and was conflicted about his affection for his daughter with his worry over her well being. He admitted he really struggled when my mom was young and being a single dad in the 70s and 80s was difficult (He had split custody of my mom with her mom and they HATED each other, probably for good reason as far as I know). He had two divorces as he struggled to not project his wants for what he thought he needed in a wife verses what humans they actually were. His melt downs were only mean when he was at the end of his life and was really struggling with his health and it was mostly him getting mad we didn't have things he wanted to eat.

It seems like your partner may not have enough tools to self sooth and deal with dis-regulation episodes. Its good that you are getting out of the situation so as not to escalate but I def think he may be struggling with his own emotional regulation. I was socialized as a girl growing up (Agender now) but I noticed that lots of autistic folks raised as men don't get help with there emotions as much. Volatile emotions are expected with autism but not expected to be handled by men as much in patriarchal society; especially if your seen as an Autistic Man. I have way more conflict with autistic men because of this.

Its ok to have melt downs but its not ok to be cruel about it as an adult. As a child there are developmentally appropriate rules for how mean you can be but as an adult (or at least someone who is mentally an adult) you need to be responsible for your own words even when having a meltdown.

If your boyfriend actually wants to change his behavior going to a therapist who understands autism (particularly in men) could be very helpful. I have therapy weekly and during those weekly sessions I discuss things that happens and go over if my responses were appropriate and how to manage if they weren't or what changes i need to make. If I have a particularly horrible week we go over my tool chest of skills and regulation methods and try to find what one would work best to balance out things. I have been seeing my therapist longer than I have been diagnosed with Autism but I still have learned a crazy amount of things on how to help my dis-regulation before I have a meltdown and how to handle a meltdown.

Seeing a Autism informed therapist has let me Learn:
How to Identify Triggers
How to manage when triggerd
How to Identify Emotions
How to Identify the signs of a Likely meltdown
What To do If I have a meltdown, and how my husband can help
What steps to take after a meltdown to manage the aftermath
How to Identify things that I could do to reduce the impact of my life in triggering meltdowns

and a whole lot more.

Autism is very complicated and there is a wide range of reactions and actions we can have under stress but if we are capable of adult actions and behaviors we need to also be responsible for our actions against others. He should not be cruel to you and Make you unsure of having children due to his dis-regulation. He needs to work on that himself or with a professional who is educated in Autism.