Please help me!!! Humidity issues...

[Skiploder]

I switched to cypress mulch after dealing (well, currently treating) with an RI caused due to very low humidity. It works wonders, without getting too moist. Glad to see you're using that.

Also, I've done the tin-foil deal with the custom lid I made, and I have to say it doesn't look too bad. It does look makeshift, but if you have the right tank I'd say it would definitely work long term.

I doubt the RI was caused by humidity in the 40% range - I think your vet is dead wrong.

As Alex advised, provide a humid hide. The risks of providing high humidty without adequate ventilation far outweigh any incorrectly perceived risks associated with moderately low humidity.