Okay. You are at the beginning of your cycle. Ammonia will rise first then drop. Then nitrites will rise and drop. Finally, ammonia and nitrites will remain at zero, and you will have a nitrate reading. This is when your tank is cycled.
I would quit doing the gravel vacs for now unless you have a serious waste problem. You can hover your gravel vac over the gravel to pick a lot of this stuff up.
I would also quit changing out the carbon. Carbon is not necessary to use in a tank unless you are removing meds from your tank. You didn't say, but I bet your are washing out your biological filter every week also (ceramic rings, bio balls, etc.) when you clean your canister. Unless the flow is severly restricted, don't touch your
canister filter right now or the bio wheel. Let them get full of gunk and don't worry about the gunk unless the water flow is affected.
As far as the water filter goes, ph is not an issue with your fish unless you are breeding, or your fish are wild caught. Most normal ph readings are not nearly as low as yours, and I believe that number is dangerously low. Your silver dollars will probably do just fine with your water that comes straight out of the tap. Unless you have some serious issues with your water supply, I would quit using the water filter. But now comes the fun part. You need serious water changes (maybe twice a day) to get your ammonia level below toxic level. Because there is probably a huge difference in the ph of your tap water and your tank water, you will slowly have to
acclimate your fish to a higher ph by cutting your tap water with the filtered water. Start slowly so that the change in ph only goes up .2 each time you do a
water change or you could kill your fish. Also, to help your fish deal with the high ammonia levels until it's brought down, use amquel plus as your water conditioner. It must be the plus formula, and it will neutralize the ammonia and nitrites, which will help reduce the stress on your fish.
I know this is very frustrating, but you can do this. Keep us posted on your progress.