Metal detector metal detector metal detector metal detector metal detector!!!!!
Those are very old home foundations most of the stuff you're finding right on the surface probably wound up there well after the place was built and used it was probably already deteriorating when it was used for a dump at a later time.
Those rocks foundations were put there well before the farm.
There's no need to be moving all those rocks if you want to find the really old stuff ... It's going to be well below the surface by now every year the leaves fall and deteriorating they create more soil... people at that time would have burned and/or buried their trash away from the home that entire area is going to have artifacts around it..like old buttons,coins,..ect.... you should really take the time and metal detect it very well if there's a water source nearby I would definitely focus around that as well