I have a water bridge on my tanks made out of 3" pvc. It's not quiet as elaborate as your set-up though. I used 45 degree elbows instead of 90 degree elbows also. The rim of the tanks support the weight of the bridge, but it's not nearly as heavy as your will be. To create the water tight vacuum, I just dunked my bridge into my large tank, letting all the air out, and sealed off one end with some wire and plastic. Then I just positioned the bridge between my 2 tanks, then removed the seal. I have a canister filter creating the flow between the tanks. I have the intake for the canister on one tank and have outtake on the other tank. The canister is rated at 350gph and the fish have no problem swimming through the water current in the bridge. I've had the bridge hooked up for 8 months now and have not had to disassemble it to clean it yet.
What I've learned is that some fish love the water-bridge and will use it all the time, while some fish don't even know what it is for and seem lost if they go through the bridge. For example, My clown Loaches love the bridge and have made it part of their daily lives, whilst most of my Tiger Barbs won't use it at all and if they do, they seem lost when they get to the other side.
myenigmaself -Goodluck with your project. It looks great so far. I'm sure some of your fish will love having the added freedom to move about.
The attachment is an old pic of my tanks when I 1st had the water-bridge hooked up. I have diy hoods on my tanks now.