The size would indicate even more that it is an American Green Tree Frog.

If he is burrowing, it could be because it is looking for humidity. Do you also have a bowl of water so it can hydrate?

As for the humidity, keep it constant around 75%. A bit above and below will not hurt at all. Temperature: Between 68 and 77. They are really easy toc are for. But make sure it has lots of room to climb up!!!

Eric