Indeed. That's barely enough to fund an Adam Sandler movie. Ironically, that would probably have been a good place to launder it.
Not sure I see the contradiction here. If he'd had time to think, he probably would have let Jesse get himself killed as that would certainly solve a lot of problems. Instead though, his instincts took over and he did the only thing he could under the circumstances, i.e. use his long-suffering car as a weapon. In hindsight (and foresight if he'd had time to think), this was a very bad move as it stood to severely damage his relations with a powerful man that respected him and kept him safe and well paid. His instincts chose Jesse.
Hearing that he was nearby watching is actually reassuring though, as otherwise his arrival at that precise moment seemed a bit coincidental.
Almost certainly Walt. Things didn't go to plan when he got to the compound, so we have to infer what his plan was, but most likely it was to get as many of them as he could into the clubhouse and let rip, most likely getting killed himself in the process. There was no guarantee he could kill all of them though, so it makes sense to phone the police in advance, giving him enough time to do his thing, and then let them clean up the mess (arresting anybody still standing) after he runs out of ammo.