Sounds like an absolutely perfect enclosure, Brandon. Make sure that you mist his cage with DECHLORINATED water and you should also have a shallow water bowl for Howard to soak in
Depending on his size, he should eat crickets(if he is small) and crickets with an occasional pinky mouse(if he is about the size of your hand or bigger...or maybe even a bit smaller.) He will also happily eat silkworms, butterworms, and waxworms. If you put any smaller frogs with him, he might decide that they look tasty and will try snacking on one of them, and chances are that he will succeed. If you get a bigger aquarium, he will be able to liive wityh another Whites treefrog his size. giant day geckos MIGHT be able to live with him although I doubt it since giant day geckos are better off living with frogs smaller than they are and since mixing species isn't very good. Temps in the 70s and low 80s would be good. You may also want to add a nice branch into his cage and some drift wood or cork bark since frogs love to climb on wood. Hope this helps!