Reference: "Tennesseans in the Civil War, Part 2".
There is a William F. Young in Company G, 49th Tennessee Infantry from which he apparently becomes the last Colonel of the regiment. The men from this company were from Palmyra, Montgomery County, Tennessee.
Same reference. There a number of William Young's or variants that served in the Confederacy in Tennessee. None of them in the 44th Tennessee. You may want to confirm the county he resided in, in the 1860 Federal Census. This will allow us to look at what units came from that county and try and make a match.
Gerald D. Hodge, Jr.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment