RE: unknown When I build memorials I just use what is on the tombstone. I don't even connect the two people sharing the stone unless it says mother and father or lists their marriage date, I instead list that they share a marker with the other. I have had them turn out to be brother and sister, so I don't make assumptions on the status.
My best advice would be just put the name that is on the marker. If their maiden name is listed, fine, but if not, I'd not address it. That responsibility falls on the researcher, in my opinion. thanks and I wish you continued success as a contributor. I find it is habit forming and a wonderful hobby that helps so many people. I know folks have been great to help me in my family tree.