Since you know when and where Andrew died, have you obtained a copy of his death certificate? It should show the names and birth location of his parents. Have you checked with the Confed Cem in Austin, do they have any records for him? There is a Andrew J. Huffman who recieved a Confederate pension from the state of TX, #33233, Ellis Co, TX. The Andrew you listed being born in 1850 would be a bit young for the Civil War, so it probably is your man. Maybe he was living with one of his married children when he applied(?) By the way, Johnston Co, OK GenWeb site has their cemeteries online, you might find Mary Jane, and other members of her family (or his).