I don't actually have info about Dennis or John PRATT, although I do know about "Ida Anna's" marriage to John WEST. My interest was in the WEST side and in the statement by some of my late relatives that my GGGmother, Samantha Jane (CUTSHAW) WALLACE, was buried in "Ann Pratt's" cemetery plot. John West was a grandson of Samantha's, which gives some credibility to the claim.
But that doesn't help you, does it? If you already know that some of the Pratts served in the Civil War, I would suggest getting copies of their pension files from the National Archives. If John died in the war, there should be a pension file under his name for pensions paid to his widow (if any) and minor children. If Dennis and Nancy raised John's son, they should have filed for that pension to help support him.
Beyond that, do get those pension files to help straighten out the relationships among the Pratts. The pension files of the eight (?) Belmont County Wallaces helped me far beyond my expectations, with the many affidavits that they filed for each other, with statements like this: "...and I have no interest in this pension, except that the claimant is my first cousin." (or nephew or uncle or whatever)