Sounds like your relationship is suffering. If it’s as you describe, in my eyes, that counts as broken.
Do you have any biological children? This child is not yours, you made that sufficiently clear.
Not everyone should be a step parent.
GP, you don’t have to do it.
I’d much rather be alone forever than treat another human being as a mere obstacle to my happiness.
Yeah, it does suffer but we make a conscious effort to find the positive things in our relationship and life.
No, I do not have any children of my own. I am thankful for that because my ex-wife apparently was also autistic but not diagnosed until after divorce. On my maternal side of the family all of us kids inherited some form of severe depression through my brother was schizoaffective. I survived, found good treatment that left me feeling like myself with a clear mind. My brother on the other hand was tortured by his demons and ended up taking his life a couple of years ago.
Not having kids was a conscious decision because I didn't want to take a chance of spreading the family curse to the next generation