Try aluminum foil to cover the screen top rather than a blanket. It's not porous, so it won't absorb or allow humidity to pass through it. It's also not flammable, so you can cover more of the top without fear that your heating elements will light it on fire.
I think that hide is very nice, but too expensive. Better to use that money toward the Exoterra replacement top and reuse a food container for your humid hide.