Hello! Welcome to Frog Forum!

There are a couple things you can do to help maintain humidity. I see you said you have half of the top of the enclosure covered by tin foil; covering the entire top will help. Just cut a circle out of the tin foil to allow for the light, leave about a 1/2 to 1 inch gap around the light fixture.

Another thing you'll want to do is invest in a digital hygrometer/thermometer. The analog ones, like what you have, are very inaccurate and will give you false readings.

Since you posted the trouble in the enclosure questions (good job!) I'd like to cover a couple other issues I see:

One major issue you have is the moss in the tank. Moss is a major impaction hazard if it is accidentally ingested by your frog while feeding. You'll want to remove it.

Crickets are fine as a stable diet provided they're properly gut loaded. I imagine the 'green cube' you described is a brand of commercial cricket feed? I only ask because I've only ever seen the powder feed and the orange cube feed. Some people have had great success keeping crickets on those but I personally haven't. When I still fed my frogs crickets I used vegetables (carrots, lettuce, and potato) and smashed up cheerios to gut load the crickets. Make sure you gut load 24 hours prior to feeding to ensure maximum nutrition for your new friend.

That said you might consider switching to earthworms as a staple diet. They're easier to keep (just put them in the fridge in the container you buy them in), they don't stink or make noise like crickets do, and they're pretty much nutritionally complete for your frog (you don't need to gut load them).

For vitamin and calcium dusting another member has a great schedule you can use which can be found here http://www.frogforum.net/food-feeder...schedules.html

That about covers it at least from what I see. Sorry if I've rambled hehe, I just woke up. One last thing is to keep in mind the people at Petsmart, while generally well meaning, are not experts when it comes to caring for these little guys and often make huge mistakes in giving care advice. There's a great thread on basic care which can be found here Frog Forum - Pacman and Horned Frogs - Ceratophrys - Care and Breeding

Good luck! You have a gorgeous little guy.