Sally, you say: "The family stayed in touch and I think a young boy just got an elderly male relative mixed up with a grandfather figure."
Do you know how your grgrandfather David Q Anderson was related to that "elderly male relative" William Columbus Anderson of Brownwood, who claimed to be William "Bloody Bill" Anderson?
If so, this can help link the Stone Co MO Andersons (David Q)to William Columbus Anderson of Brownwood, who some claim could not one of the Stone Co Andersons, as he was the real Bloody Bill.
Could your David Q be the 15 yr old DQ with 9 yr old brother WC on the 1850 Taney Co MO census? With other family members that do not match Bloody Bill's known family?
Researching and identifying both William Anderson's family groups was the key to proving who the real Bloody Bill was and was not.
I personally have not seen David Q's name spelled out, but a good place for clues is the mother's family. Next, I would suggest the custom of naming sons after Presidents, and since John Quincy Adams was President from 1825-1829, that may be a possibility as David was born about 1832. Next, I would suggest the custom of naming sons after a local family friend, or a person who held high esteem in the community.

Sincerely,
Fran Bolton