First, go shut the water off at the nearest shutoff valves for the hot and cold or the entire house if necessary.
If the second wrench you got is a faucet wrench that has a half round toothed edge that swivels, then that should do it. Use a cheater on the bar that slides through the handle. Spray some wd40 on the faucet nut.
Is there a short hose going from the stop to the faucet or is this one piece of pipe coming out of the floor? Remove the hose at the lower connection if it has one.
If the faucet nuts can't be loosened, then a plumber would probably cut the line and install stops if this is a direct connect.