Matt, You are on the right track using a combination of heat, cold, and penetrating oil. First, understand that I do not have one of these carbs with the rotating heat control, but I do know that this part of your carburator is unnecessary to operate your car. Modern gasolines do not require pre-heat to run properly, it will just take a bit longer for the engine to warm up. I would first use PB Blaster penetrating oil to help dissolve the corrosion. Give it time to work overnight. Then heat the outside of the casting and cool the internal rotating part with ice (dry ice works best). Add more oil just before trying to move the parts. All three in combination should eventually free the parts. Just be patient and work the moving parts back and forth in very small increments. You may have to repeat this over several days to get this done.