As far as Kelso’s Company, the details are a little sketchy to me. If Steven Mayeaux is watching this thread, he might fill in a little for us. His book, Earthen Walls, Iron Men,” which I believe is available by a link on this web site, discusses John Kelso considerably. Kelso commanded Ft DeRussy until Feb of 63.
My guess would be that when Kelso returned to Louisiana from VA he then formed “Kelso’s Co of Heavy Artillery.” According to the National Archives “Records of Events” the organization was on Dec 5, 1862 and I would guess at the fort. Dr Bergeron’s guide says that Kelso’s Co along with King’s Battery joined the 16th Bttn at Alexandria in June of 63. It appears to me that it may have been at this time that the company became infantry because the records say “formerly Kelso’s Co. La H Arty.” Possibly any artillery assets it may have had remained at the fort or were transferred to King's Battery. King's continued to be a viable heavy artillery unit.
In November of that year the company was consolidated with the Crescent with 14 men going into Co A, 16 into Co E and 15 into Co I. From that point on the original company no longer existed.