My daughter was 6 months old when we got married - does that make a difference to my estranged husbands rights?

The only real difference would be that since you weren't married at the time of birth. Then he isn't the "presumed" father of the child. In that sense he may have to assert his rights to the child. But he still has the full weight of the law backing him up.

Its just proceedural.

Califdadof3 is absolutely right. He is the putative father and not the presumed father, but were he ever to exercise his rights, he would would probably have immediate joint legal custody and can pursue physical custody if he wishes. In some states, as long as you were not married to someone else in the 9 months preceding the birth, your husband at the time of birth is presumed to be the father.

I guess first, is he the father,