After you file

Yes it sounds like he is trying to claim you as a dependent.  A spouse is never a dependent.  Do you have child you are claiming?  Maybe he’s trying to claim the same dependent as you.  You need to have a qualifying dependent to file Head of Household.   Do you live with your spouse or apart?  If you live together you can’t file Head of Household.   Double check his return that it is Married filing Separate.