a few questions

ok the bike will be find after the spark plug and you need rear brake pads when you are going threw the medal of the shoe
 
You need to change the brake pads while they still have a little friction material left on them.

If you run them to metal, damage can be done to the disc!
 
You should be good. You didn't run the plug that way to long. As for the brake pads, you have to look at them to see how much brake padding you have on them.
 
No the bike will be fine and the way I know is to look also you'll need to check obviously when they begin to squeek and stopp less seddenly. ok