Plumbing remote sump: 90s ok?

[sphelps]

Run 1.5" for all three lines, 3/4 return is would be silly for a tank that size, would expect a plumber to know better

You can use the head loss calc on reef central to estimate total head pressure and while frictional losses are totally dependent on the pump flow rate the pump you'll probably want will end pushing close to twice as much flow through 1.5" vs 3/4".
http://www.reefcentral.com/index.php...oss-calculator

Also I don't see any issues with horizontal runs and a herbie drain. All lines should have some slope back towards the sump for drainage and the sump needs to be large enough for the back flow. Other than that, not much else to consider.