If you tell him how his words make you feel and he keeps on saying them, then yes, this is abuse.
Did he have a similar pattern before the DCs were born?
Was there anything that he criticised you for before?
If you told him to stop and told him how that made you feel, did he stop? (Assuming there was something he honed in on).
If this is something that has only happened since you had DCs and he became father of a family, then it is not autism.
There is a bit of cognitive dissonance going on when you can say, in the OP:
Generally I'd say we have a great relationship-it was certainly great before we had kids. He's still loving, supportive & a good dad.
But he has a habit of saying hurtful things about how I look.
This especially must jar with everything you want to believe:
I feel like he hates me.
I can cope with the fact he's not one for compliments
But it's not ideal, is the subtext there, perhaps?
Would you like compliments?
Or would you settle for no more disgust expressed towards your body?
He did apologise but in that conversation mentioned my belly, the fact I've put on weight & said he loved me anyway (like I'm a charity case & he's doing a good deed). Then a few days later he mentioned my stomach sticking out.
You must have registered some response, or he wouldn't have given the non-apology. Did you confront him?
This episode when he didn't actually apologise and actually held his ground, and then basically did the same thing again a little while later should show you that he isn't interested in building the relationship, or your feelings, or anything but wallowing in the reason he is in this relationship at this point (whatever his intentions may have been initially). What he is getting out of it now is the chance to be cruel to you.
This is how things have become such a mess. He has chosen this. This is what he wants.