Excellent description of your setup! Question about your sump tricks including the sponge tray - in addition to reducing noise, does it also reduce splashing of water droplets? I have a problem with salt buildup due to droplets from skimmer return, emergency drain, and flow into return chamber. I may also try your under-tank fan idea in the future. Thanks for posting all the details and photos.
Yes. Definitely minimizes splashing as long as the water isn’t falling from too high.