I didn't address your idle problem at all. Your idle problem is the least of your worries anyway. Your gonna have to fix the compression first. Im thinking once you freshen up the rings and valves all this goes away with your ldle problem anyway. Probably wants happening is the total condition of the engine is weak and all the rings and all the valves are not up to par. In total when one cylinder went totally dead that put enough strain on the rest of the engine. When you put oil in cylinder #7 it went to idling ok again. That's because the cylinder came back for a few minutes. The vac signal from the engine to the carb is weak thus causing the carb not to get the correct amount of vac signal thus causing the engine not to idle properly. The carb is not stopped up. How I know this you said it ran fine when you put oil in #7 to make it fire again. It's no big deal. 99% of the time a dead will not cause you a real bad idle. But I think in your case. I thank the total condition of your engine is causing you a to have a bad signal. Carb can not and will not operate correct if its not getting the right signal from your engine.