Anything that has a relatively rough surface. A sterilized rock or branch from outside, or any of the fake branches and such that you can find in the reptile section at a pet store are usually the best choices. Just be sure it doesn't have any sharp edges
yup a second heat pad would be fine as long as it's regulated on a thermostat so it stays at the right temp. I'm not sure what you mean by the "top temp." Ball pythons usually stay on the bottom of the enclosure Both heat mats (belly heat) and lamps (back heat) work fine for them so switching from one to the other won't cause any problems
I keep mine on newspaper and once there eyes go back to clear I mist daily and 99% of the time they have a complete shed. the only thing they have to rub against is a water bowl and it has smooth sides.
They really dont need anything rough to rub against if it has good humidity...the only time they rub against something is when they're trying to loosen their skin...