Whoa could you get those pics any smaller?
You have a couple of options for your stripped 12mm nut problem. 1 is get a big pair of vice grips (locking plyers) and clamp that mofo on there REALLY tight. Might want to have someone strong clamp it on there for you if you can't. The 2nd option is you can buy a "nut buster", they are like $10 from the parts store and work pretty good, they destroy the nut, but at least you can remove the part and you can always go buy a new nut. I have one right here next to me and if you want I'll post a pic of it.