You should have 3/8" between frames, any more and they will build a lot of burr comb. From the looks of the burr you show, it appears you have excess. Different manufactures layout the space differently, some will put it all above the frames, some will split it top and bottom. This can lead to issues when using different manufactures. I assume you bought it all from the same place, so I would measure it and then talk with them.
Same goes with the vent box or inner cover. Anything more than 3/8 will cause headaches. As far as screen on the center hole, I would highly suggest removing it. Without the bees being able to patrol that area, all kinds of spiders, ants, earwigs, cockroaches will take up home in there. You have to really cramp the bees for space before they will build comb up there. The restriction is too small and breaks up the nest to them, so they will resist it as long as possible. I been using them for many years and have never had comb build in one.