Jimmy,
Your on the right tract!!! Mine was a mini fridge and is only half the height. It didn’t have any info like yours and the manufacture would not provide any info due to legal reasons. Lets start with what you have. You’ll only need one fan going to the terrarium to push or draw the cool air into the tank, a 4 inch fan is far too powerful for this setup unless you use a speed controller. A 30 or 40 mm fan will be enough. Too much fan will really over work the fridge. You'll still need a small fan inside the tank to circulate the air during daylight hours. Next I like the idea of the drip pan and would suggest insulating the two sides, back and top of the terrarium with half inch silver coated insulation board. This will also cut down on the condensation. Speaking of condensation, your going to get a lot in the fridge when the warm air from the terrarium hits the fridge. I would raise the fridge off the floor 6-12 inches, remove the drawer, silicone a piece of plexiglass in the lower front of the fridge. Just like you did with your other terrariums. Then I would install a bulkhead fitting and hose in the bottom of the fridge to drain the condensation. Your going to need a heavy duty timer to turn the fridge on and off at the desired times, and some type of temperature sensor probe to turn the fridge on and off then the desired temp is reached.
Your going through a lot of work and expense for this project, but I feel you will soon out grow the size. You never have enough tanks or space in the tanks. The fridge is a very sturdy platform. As long as you provide adequate support such as two sheets of ¾ inch plywood with legs on the outside corners you could mount almost any size tank above the fridge. Or the fridge could be stationed next to the tank and not underneath it. I use a Critter Tank, its 16”x 18”x 36” one end is only glass on the bottom half and a plexiglass panel filling the rest of the side. Its half the price of the same size fish aquarium. I use mine in the usual orientation (open top up) with a three sided 24” plexiglass extension. I use a glass top to reduce warping under the lights. I duct my fans, drains, humidistat wires, heater wires, drain tubing, and air line tubing through the plexiglass. By using this type of tank you wouldn’t need to drill two 4” holes through the glass. You could turn the tank on its side like you did with your other terrarium, dam the front, install sliding glass doors and dam the lower part where the removable plastic panel goes. You would still need to drill the bottom for a drain line, but that would be the only hole you would have to drill in any glass.
By the way the Hummer’s Giant picked up and is doing well. I’ll send a picture when I can take it outside. Yesterday it was 85°F today its snowing.
ccgpro