Interesting that you specified 1863 and 1864 in your question about Texas State Troops of Titus County, TX.
I have a listing of about 350 men who first enrolled near the Louisiana line in late 1863 and 1864, then served west of Gainesville, Cooke County TX. ..It is probable that most - due to a sense of duty - followed suit and got on their horses and rode to North and West Texas where they either formally or informally formed a militia (maybe without pay or record) to protect their fellow Texans. Many came home and moved their families to North and West Texas. ..Sometimes they only stayed 6 to 8 weeks.
I submit that this is a major contribution to Texas history that crystalized because of the of scope of my detailed study: the area between the South Canadian River, I.T. and Dallas and the Louisiana line to (now) Childress County down to Jones County, TX.
My records show six men named Keith that may be your "J.H. Keith" of the Titus County, TX area. ..Do you have his full name? other Keiths of Titus County?
My 134-page Name Index has several Bartons in Lamar and Red River Counties, which are near Titus County.
Please send me the skinny about your Keiths and Bartons of the Titus County area in the Texas State Troops. ..We need help on makng sense of these fragmented records.