Congrats Jeremy! Your new baby looks great!

If you give it a bath, 15-20 minutes is fine. After that the water is going to cool down even with the light over it. Since you are just using the tuperware as a temporary enclosure for the next couple of hours, you should be fine with either the paper towels or some substrate. If it starts acting stressed (jumping and trying to climb the walls) then switch to the substrate. Also, I can't stress enough that you must use a water conditioner to de-chlorinate the water (including any water you use to expand the substrate). Otherwise the frog will tox-out.

Let him be for the next couple hours. Offer food tonight. I almost guarantee that s/he will eat. I would go straight for the nightcrawlers. Cut off an appropriate sized chunk and offer it from tongs. If s/he won't accept from the tongs, you can put a couple crickets in the enclosure. Break the back legs off so they are easier for the frog to catch. Remove any uneaten crickets in the morning.

Congrats again and keep us posted!