1c ) checked with all tank makers in singapore , all uses grade 1
1e ) 10mm ( my tank volume same as you, & all 3 tank makers says 10mm is more than enough even for marine )
3a) pinwheel pump is the pump that feed the skimmer. comes with it if you buy internal skimmer type
6) for arctica chiller , i would say 1/3 HP.
7) no need heater , those reefers in cold country(angmo) then need heater .
9a) return pump - eheim ( reliability and better max head since you going sump)
feed pump for skimmer - if you buying internal skimmer , pump already included