That filter is plenty large enough - it’s huge! I have the same one for my 25K gallon pool.
Filter pump: Is that a variable speed pump? If not, I strongly recommend one.
Ditch the cleaner pump and the Polaris. Get an electric robot instead, which will do a better job of cleaning and cheaper than the pump, associated plumbing, and Polaris in your bid.
2 skimmers and 5 returns: those look good. It’s very useful to have 2 skimmers, 1 at each end of the pool, because wind directions change.
As for decking up to the foundation, I left a 2’ wide strip open and put artificial turf there, which is porous and will let water through. It looks great and is comfortable to walk on. I almost wish I had made the turf area larger as another “yard” area.