- yes, flexwatt is safe to put on plastic as long as it is controlled by a thermostat

- I think feeding him should be your call. if he were mine, i'd try an appropriately sized prey item, and then get your tub set up while hes given the 24-48 hours to digest his food. Then, wait another 5-7 days before trying to feed him again. I would start the acclimation period over again (the 7 day settle in time) once you put him in the new enclosure.

- some activity at night is normal, but frantic activity also during the day could mean that he is stressed for some reason.

and just for other notice, on this website people like to have accurate information about the set ups, actual temps and humidity, not just "fine". And based on your post..his heating element isnt on a thermostat? if this is true its dangerous.

good luck with getting him into his tub