The crush washer on the spark plug should be removed if you are using a temp gauge.
To do a reading of the plug the portion we are looking at wont tell you much. Basically if you look all the way down into the inside it should be a tan/milk chocolate color, black is rich and white is lean. Doing a plug chop is a fine way to tune, but I don't ever do it. I just start with a fat jet and work my way down then dial in the needle after.
Rich sounds like it is under water, the sound it makes is called four stroking. It is actually taking 2 full rotations of the crank to expel the fuel charge in the combustion chamber.
For the brakes it looks like you could use some new brake shoes, I would get a new set of cables while youre at ir. Also make sure the pivot points arent binding and the springs are intact.
The choke on a bing is for cold starts. You push it down, start the bike and when you twist the throttle it comes up and should stay up.