I am not using that fridge as part of the setup anymore. I needed more taps. I was however using a few fans inside the keezer. I found that having them mounted to the collar with an alternating pattern of pushing and pulling air at a angled horizontal approach to work best. Make sure you use bearing fans and not bushing types for horizontal mounting, bushing fans wear out quickly when horizontal. You can use metal angle L brackets to mount the fans.
I did get a little condensation in the bottom of the keezer, but no more than most. To stop the pvc pipes from dripping I wrapped them in Hvac foil backed pipe wrap insulation. This really helped.
The extra insulation in the box was for the extra airspace, there was no need to have. The block in the middle was a piece of Styrofoam that I wrapped in foil tape. It helped reduce airspace and direct the incoming cold air right over the tap shanks.
I would recommend that anyone who builds this seals the area where the pipes go through the collar with silicone. I found a little mold on the wood when I pulled it apart.
See the pictures attached for info about the fans.
Hope this helps. Feel free to ask more questions.