Keith: I have no way of knowing for certain that the Capt. David Reed that surrendered with the 15th MO Cav was the same as the Waybe County David Reed, but I suspect that they are one and the same. Some members of the company he commanded in the 15th appear to be Wayne County men. After service as a companpy commander in the 2nd Cav Bn, 1st Division, MO State Guard, David Reed of Wayne County commanded a company in the 2nd MO Cav Regt (McCulloch's) that went east of the Miss River. He and most of his men eventually deserted and returned to the Tran-Miss. He raised a second company that at one time attempted to attach itself to the 7th MO Cav Regt(Kitchen's), but I cannot find that the attachment was ever approved. Since he continued to operate in Southeast Missouri and Northeast Arkansas, I think it likely that the company finally became part of the 15th MO Cav.
Like Bruce, I have not been able to identify Capt Howard. However, it seem unlikely to me that Reed, who had always been a captain of a company, would subordinate himself to someone else and serve as a lieutenant.
Just my thoughts.