Seems like there is a lot of wasted space on this sump. The pumps should be all the way to the left. the water should have to flow through the carbon and zeolite to get to the pump.
Most hobbyist will tell you that zeolite and carbon are not essentials to every day filtering. Those you would only put in as necessary. There's no need to dedicate a specific chamber just for those two. UVs help, but I would only use one if you need it. A lot of people put them in-line with the pump.
That wall you asked about is both to put a final (polishing)sponge in - also the sediment and sludge that inevitably falls from the media cant go back into the tank