Hi Jay: In the book on the KRR NY with the Master Muster Roll prepared by Gavin Watt, it shows the following -
McDonell, Donald KRR NY Battalion 1, Inlistment date 18 Aug 77, Discharged 24 Aug 77
This is the only Donald McDonell who left/died in 1777 after the Battle of Fort Stanwix.
It could be that he was injured badly and sent home to be cared for.
There is no notation of a wife and daughter.