Idle acting crazy

This is a recent development with the way my car is idling since it has started getting up into the high 80s in NC already. I had vapor lock issues last summer & thought I had taken care of them but it is acting up again. I can't have the car not drivable when it gets hot or I won't be able to drive it again until October. I have replaced just about everything I can, new 1/2" spacer under new Edelbrock 1406 600cfm 4 barrel carb, new fuel pump, fabricated a heat shield to put between fuel pump & exhaust, insulated the fuel lines, new fuel filter & put a 180 t-stat in help it run cooler. The car is not running hot at all. The car is a '65 Barracuda with an early 70s 318 auto in it. The motor was in the car when I bought it so I do not know that much about it. Converted to electronic ignition last winter.

The issue: When I am sitting at a light in traffic the idle is around 500 rpms, as I am sitting the idle starts to drop until it is barely chugging around 200 rpms. If I slip the car into neutral the rpms start to very slowly climb until they get back up to around 900. I have also noticed that sometimes when I turn the car off the clear inline fuel filter is empty. I think I am still having some sort of vapor problem. Is it possible that the fuel is cooking in the line while I am sitting at a light? I really need some help here guys! Thanks ahead of time.