In my mother's extensive notes on the George Abbott of Norwalk line I find: Charles S. Abbott born c. 1866, died 16 Sept. 1908 age 42. Served in Company M, 1st Infantry Connecticut Volunteers, Spanish American War. Is this the Charles you mention?
She also notes that she believes he is the son of Daniel S. and Mary who appear on page 1010 of Major Lemuel Abbott's tome; she believes therefore he is in the Robert Abbott of Branford, CT line, not the George of Norwalk line.
I realize you entry is over 10 years old, but perhaps you can verify or refute her contention.