I definitely agree with you on the sump height. Dude I got the whole setup from made it from a aqueon 29 gallon. I thought and still think it's way too tall. Guy who had it, had the sump right in the middle of the stand which didn't lend much usable space. I needed to have everything inside the stand. Thought about getting a 20 long and using that and likely will later on. For now im trying to stay within a budget and work with what I have. Since I still need to get an RO system. As for the return I ended up putting another street 90 down that's 1in slip to 3/4 thread and bought some loc line. I seen the U shape return nozzle but felt iffy about it.they sell U shaped return jets that u can hang over the glass and/or use modular loc line to aim where ever u want. https://www.bulkreefsupply.com/pumps-plumbing/plumbing/loc-line.html
Nice job with the sump build and plumbing... one concern I have is how tall the sump is in the cabinet w little room to reach inside sump for maintenance, is there enough room to remove skimmer when its time for cleaning?