MAG9 + Plumbing Qs URGENT HELP!!!

[xexxxe]

Hi, I am a newbi trying to set up a 75G tank with 30G Sump...

This is what I have so far...

1. 75G reefready tank with 1" to sump and 3/4" return overflow built in...

2. I have purchased MAG 9.5 for return pump.

with about 4.5ft of head... MAG 9.5 should have 800gph... and it seems like i have too much power on return...

I am currently hooked up with hose for all plumbing... 1" to sump and 3/4" return and I have a bad feeling it will overflow the tank when i go to sleep... so i decided to umplug the system...

is MAG9 too much for my setup? should i reduce the return(how?)

I got the oceanic 75G RR... and I saw it somewhere that the overflow is MAX 800gph...

should i change it to PVC pipe for plumbing? if so... what size?(inner diameter/outter?)

would valves for piping slow down the return GPH? will it affect the pump.... or should I just get MAG7...

I don't know what to do... plz help...

if anyof you have any good way to set up plumbing plz help...

THANK YOU for LOOKING