I'm not sure the spacers needed but it is cool and shows your ability,
Psi measurement isn't asomething I factor into a loop normally, the pump will provide sufficient pressure throughout and my brain doesn't need to know the math, as long as its flowing 1Gpm or thereabouts it all good,
I hope the EK Gpu blocks aren't Nickel, if they are then Google EK Nickel problems just to read up on the issue,
A cpu and 2xGpu loop is likely to need more than a single 360 rad though, have you read through the sticky to find out how to calculate your TDP?
Sticky is at the top of the section and is full of useful info to check out
Moto