Help with Fuel return line

in short "no"
slightly less short, "heck no"

the reason you have two ports is because you can use that regulator to run a dual carb setup
or if you wanted to, you could run a double pumper and run one line into each bowl from the regulator

what you can NOT do, is run that line back to your tank, because both sides have the same pressure, and since the fuel will take the path of least resistance it will run right back into the tank, giving you hardly any pressure at the carb

a regulator like the holley 12-803BP would work for what you want to do