The probe from the acu rite should help you get a good reading right on the bottom above the UTH. I don't have personal experience with tubs, so I can only tell you what I have heard. You can put the UTH which ever way you want really although the second pic is how mine is set up on my tank.

Newspaper is easier to clean, although not as attractive, but as far as getting better readings by switching to newspaper, I don't know if it matters much. As long as you get a probe or thermometer to read the warmest spot your bp has access to (so if you keep the substrate, you want to know how hot it is right on the plastic because he could decide to squirm his way down under the substrate and cook himself if it's too hot under there)

Your doing great, I don't know why you haven't got many responses. I'll try and help more if I can.