zanemoseley,
The drainline from the fuge back to the sump can be submerged in the sump side. It will not get "airlocked" as someone else mentioned.
I don't understand what this air lock is anyway.
Water will fall through the 1" bulkhead fitting, through the 1" drain, into the sump. No problem. This is the way I have mine set up. These is no airlock issue to worry about.
The one thing I would do differently from your original design is this.
On the line feeding the fuge.
It MUST empty out into the fuge "above" the fuge water level.
Since the fuge is run at a higher elevation than the sump - if this line is allowed to enter into the fuge water - when you lose power your fuge water will siphon back to sump.
Just as we need a siphon break on our display tank returns - we also need a siphon break on the fuges return.
This I know from experience and dry/wet run testing.
Other than that - you may find that the overflow drainline is too far under water. It's true that if it's underwater, it most likely will be less noisy - but it may slow down your overflow rate some. You can still have it underwater - just have it barely under.
Here's what I was talking about with the fuge level and the fuge return emptying out "above" the fuge water level.
Looks good to me otherwise