It does look like an American Green Treefrog, Hyla cinerea, but you also have the similar looking but rarer Squirrel Treefrog, Hyla squirella, in Arkansas (Herps of Arkansas: Frogs).

Check your local laws about the legality of keeping it. Generally speaking, pulling adults out of the wild breeding population is not ideal- it removes them from the breeding population (not a major concern in small amounts from a thriving species) and it's harder for them to adapt to life in captivity. It sounds like it was in rough shape and that's great you helped it recover! I'd suggest letting it go if it seems to be healthy now, and if you're interested in keeping a frog aim towards collecting a younger one (even at the egg/tadpole stage next spring) once you had a permanent habitat ready to go. But it's up to you, probably most if not all of the Hyla cinerea​ found in pet stores for sale were wild caught.

Care for either is mostly the same as a Gray treefrog- Frog Forum - Gray Tree Frog Care and Breeding (Grays are much more cold tolerant though!). The higher the tank the better, but a 20H would be large enough. I've no experience housing them with fish, and personally would just set up a dedicated treefrog tank as more tanks means more fun.