I too am searching for ancestors to a Gideon Allen.He was born in 1804. We know he lived and acquired property in Twiggs County GA. He's listed in the 1830 and 1840 census and through familty letters we know he left in 1845 to settle in Bossier Parish LA. I have much information after that time, but little during the time he lived in GA, and nothing prior to 1820. We believe he may have come from an Allen family from NC.
Several of the names you mention show up from time to time in our family names. What is the date of births you have recorded for your Gideon Allen, Jr?If there's a match, we may have a connection and I may be able to fill in some missing information.