1" bulkhead going straight down is rated for something in the 600 GPH
Never rely on your return/filter pump for water movement. Your protein skimmer is a beautiful piece of equipment that will seriously help improve your water quality. You want water to move SLOWLY past the skimmer so it can collect more particulates. Ideally a skimmer is also after mechanical filtration. Water passing through a refugium would also be better off at slower rates. I recommend aquarist AIM for a 5x turnover rate in the sump.
Try to use flex tubing as this will decrease micro bubbles and is just easier to work with imo
. I would use 3/4" flex on your overflow from the 1" bulkhead after an immediate 90 degree
I wouldn't want a loud expensive vibrating pump when it's not necessary for most applications.