I am a little confused here. So you cut two large holes in the lid, covered them with screen, and then covered them with aluminum foil and duct tape?

Is there any ventilation?

With tubs, we put lots of small holes on the sides of the tub. Any holes on the top will reduce the heat and humidity pretty significantly.

I make holes with a soldering iron but you could also use a drill, a wood burning tool, or a hot screw driver.

As for your temps. an ambient temp of 75* is perfectly fine if you have a hot spot in the low 90's.