Allright I just pulled the plug, and it slightly wet from what looks like oil. Probably from when it was upside down. The center of the plug that should be white to light brown is pretty dark brown. I also noticed that the plug is missing the screw on top, it just has the threads, and the gap is rather large at .025. Looks like we got oil up to the spark plug while it was upside down.

 

Forgot to ask who carries replacement plugs? The plug is an NGK cr8e. Maybe Walmart or Pepboys?

 

What about the rest of the questions?

I would buy a new plug and see what that does. Let us know if it cures the problem