Although this may sound stupid, you have to dig the trash to get the good stuff. Years ago a bunch of the guys in my club including me were hunting a local lake. We hit this spot that we thought would be a good spot to hunt in the water. It took us over a month of hunting that site before we finally started to find the goodies. On the average we took a 5 gallon bucket of junk out of this site everyday for a month. We still take junk out of this site. But we also found over 500 rings at this site and many, many Silver coins. Also many necklaces and other items of value.
So you see, You Gotta Dig the Junk sometimes to get the goodies, now that you have all this junk out of your yard, go back, slow down and hunt those iffy signals. You might want to try hunting in coins for awhile and use about 4 notches of sensitivity. On the signals that only sound off going one way and not on the return swing, the item probably will be an iron object.
Good Luck and remember, keep the coil to the soil, Ringfinder
P.S. I also use a ACE 250