I'd move the gauges so they are close to the ground where the frog is because the temp/humidity will be different near the substrate. A screen lid is fine and so is a glass one, but if the humidity won't stay up there you should put some foil or plastic over most of it, except where the lamp is of course.

As for his size, I dont know really. I've had my frog a month and he hasn't grown at all and hardly eats. Guess we should work on plumping are little guys up!