Dart frogs areterrestrial Sometimes they will start calling before lights on and after lights out.
For drainage, I have a corner where I can lift the screen material that seperates the drainage area and substrate. I use a aquarium siphon hose and have the collection bucket lower than the tank so i can get it draining with suction. Stole plenty of gas when I was a kid.... only kidding :-)
You can use a pump like this one : Walmart.com: Battery-Operated Liquid Transfer Siphon Pump: Automotive
Or you can have the tank drilled and a drain valve added.
As for what you have, that should be fine as long as you cover about 90 percent of the screen top with clear pleni-glass (available at lowes for about 6bucks and cut by them to your measurements free) or a piece of glass.
Just want to make sure enough light gets through the screen to service the plants needs.