It sounds like you've got all the help you need in obtaining a VA stone for Lindsey. I don't know why the VA is now asking for birth dates as this information is generally not available in CW Confederate records. If necessary, you should consult the 1860 Federal census. His records give two ages 25 & 27 on enlistment

George Martin

Lindsey P. Partridge, age 27, enlisted for a period of one year as a Private in Captain J. G. King's Company,(Old) Company G, (New) Company I, 8th Regiment Mississippi Volunteers** October 18, 1861 at Enterprise, he had originally enrolled for State service on April 15, 1861 at Rushing's Store with his age stated as 25, recorded as sick in Hospital near Tiners (sic) Station, Tenn., August 31 through October 1862, died of disease in Hospital November 17, 1862 at Cleveland

**"This company was transferred from State to Confederate Service with the 8th Regiment Mississippi Vols., Commanded by Col. G. G. Flint,for their unexpired term. This Regiment organized on the 24 of August and their term of service commenced on that day."
[Compiled Service Records M269 Roll 172)

Tiners/Tyners/Tynervile Station was located midway between Chattanooga and Cleveland on the East Tennessee & Georgia RR