I honestly don't know much about tree frogs (terrestrial frogs are my thing) but those temps seem a bit on the low side to me... I know with a lot of terrestrial frogs 80 is a good temp, and keeping the temps up helps with their digestion.

Since he's on paper towels I don't think he could get impacted, especially if he's accepting food. An impacted frog will stop eating.

Someone more experienced will chime in. Best of luck!