Sorry to keep asking for help but I thought I would have all these issues sorted before the snake came home and I am having some issues

So just 2 questions please and then I think I can truly move forward comfortably.

1. Adding heat tape - can it be taped directly to the bottom of the pvc tank or does there need to be a gap between the tank and the tape?
How do you acheive a gap if needed?

2. My radiant heat panel is not keeping the tank warm enough by itself (therefore adding heat tape); should I buy another thermostat so each has it's own?
Or can I just attach both to the same thermostat and set it for very close to the high temp wanted; placing the probe on the "hot spot" substrate until I am sure they are working together well?

Please help!