Samuel appears to have been the only one of Isaac's sons' who did not become a loyalist. (Letter from Nancy Otis to Alan Salls dated 5/20/2002.)
Gravestone photo from Nancy Otis.
There is a Samuel Salls listed in New York in the Revolution as Colony and State, Vol. II, originally published in 1897 as being an enlisted man in the 17th Regiment, Albany County Militia. This is probably the same Samuel.