All Small Six Engine Stalls After Heating Up

This relates to all small sixes
1966 Mustang 200cid engine with Carter YF 1 barrel carb. I recently had some ignition problems which were resolved by replacing PCV, Plugs, and cleaning the distributor cap. This weekend I was driving in the Connecticut hills and after driving for ~10 -15 mins, if I let off the gas pedal and let the engine idle it would slowly decrease rpm and stall after about 10 seconds as if the engine was flooded. I would not be able to start it again until it cooled and the system drained, or if I held the throttle down and then cranked it (after tinkering with the mixture screw and using some starter fluid... Not ideal I know but it was midnight and freezing at a gas station and I needed to get back to the city.)

Not sure where this issue is coming from, any pointers would be great. My online reading indicates a fuel filter issue, float issue, or there is dirt in the needle. Too cold outside to be vaporlock.
If it is cool and damp out, it could be carburetor icing. Look to see if there is ice formed on the inside of carb. If that is the case you need to get some heat to the carb.
Ignition switch can act up after a while.
It sounds like you have ruled out potential flooding since you had to use starter fluid; Something that would make to condition more difficult.
Late night driving and in freezing temps, I assume you were using the blower on medium or even high; then you were definitely drawing additional power through your ignition switch and fuse panel.
Look for some lower-than-normal voltage drop. You can also use your fingers/hand to find problem spots along your electrical circuits and components, i.e.- your ignition switch can feel warm after running a while with everything on but if it's hot to the touch you have most likely found your problem area. Be sure to look closely at the terminals and wiring going to it for hardening or discoloration. You may have to fix those also. Note that the blower resister will be hot to the touch because of what it does.