Careful with the infrared light, it'll evaporate the water quickly and could dry him up if you don't mist him often.
I'd recommend an under tank heater for heat. exo-terra makes those aswell.
Don't use aspen, the oils may be bad for it's skin, and it'll go rotten fast.
Most importantly, aspen and woodshavings are designed to absorb water, and you want it nice and wet. If you must, use potting soil.
As someone did mention, just be careful and make sure it has no white dots, check the label.
Frogs are an extremely sensitive indicator species, which essentially means
that their skin can react to even a slight trace of chemicals.
Potting soil wouldn't be good for it to ingest.
I recomend eco earth for substrate, exo-terra makes it,
It's sold in a brick, it lasts a long time, it usually goes 6 months before beginning to decompose, it's only 5 bucks for a brick that'll fill a 5 gallon.
Add sphagnum moss and most importantly a shallow water dish.
Sorry i replied to more than the questions you asked.