Everyone has specified what you need so I will address the heat pad.

Any UTH should be appropriately sized for the enclosure you're using. If you're going to switch to a 5 gallon then you'll want a heat pad for a 5 gallon tank. Zoo Med labels their packaging with the size tank each size pad is designed for so I would look into their UTH, but still be sure to place it on the side.

They're smart in terms of thermoregulating their body, but if you place a UTH on the bottom of the tank and the frog becomes too warm or its favorite burrowing spot happens to be in that area the frog may be burned on the glass or overheat themselves due to these frogs burrowing to thermoregulate and the frog will not understand why it isn't cooling down when burrowed. Basically it confuses the frog and this can result badly.

Your frog isn't hyperventilating, its just scared. Also ambient air temp should be 80° during the day not just the warm side, but the air temp of the entire enclosure as well as the ambient air humidity needing to be 80%. Would should be moist or heavily damp, but not mud.