An additional note: when using the wet sanding sponge, it seems to only make the poly coat gummy. I even tried to sand off the gumminess with 220 grit and it's not coming off.

You don't really want to get the poly coat off...you just want to dull it. The poly will likely turn to a thin layer of dust so you know that you are getting where you need to be. Wet sanding doesn't work. It's one of those things that people say does work, but it doesn't. The sanding blocks most of us use are made by 3M and are either fine/fine or fine/medium. The pads are fine grit and are also made by 3M.