You've got a big pump which bypasses a lot of fuel. Compound that with the fuel running through the heated fuel rails before being bypassed to the tank. There are a couple things that would help a lot.
#1 Get the regulator bypassing
before the fuel rails. That way the engine doesn't get to heat all the fuel.
#2 You may need to install a pump controller on that pump to lower the voltage during cruise/idling conditions. This creates a lot less heat in the pump and heats the fuel less.
#3 Install one of these nifty cool cans on the return line to the tank to cool the fuel!
Jody