it's not that hard to take the top of the carb off and check the floats and float level. It's easier than taking out the plugs which you managed to do OK.
If this issue is carb related, or related to the stabilizer, after cking the floats, you should just put in a new set of plugs, a tank of FRESH gasoline, and DRIVE THE CAR for at least 45 minutes at highway speeds. This will give it a chance to blow out any accumulated loose carbon, and give you a much better idea of what is going on.
btw, it's not unusual for certain cylinders to be more prone to carb fouling issues. This can be due to different compressions, excessive clearances, etc. The cylinders that haven't fouled, would probably do so eventually, if it is a carb problem.
Just so you don't forget, DRIVE THE CAR MORE, please.