Yeah right, MAD is a deterrent not a first strike weapon. Besides that, asteroids spend most of their time extremely far from Earth. If you launched some mega project to get out there and redirect one that wasn't already headed for us it would take you years of preparation and then years of execution time. Your enemy could easily see all of this activity and decide to just start a conventional war in the mean time to take you out and still have enough time to deflect your war asteroid. It's a dumb scifi plot device not a practical weapon.
You'd need a very, very big explosive for any but the smallest grains to have divergent paths. They would form a cloud of debris that would travel on the same orbital path but spread out a bit. Breaking an asteroid up only works if it's fairly small to begin with since anything over about 50 meters that is solid is still going to be dangerous. If you broke a 2km asteroid into a mixture of 50m to 100m chunks of solid rock or metal then you're still going to have a very bad time when all that debris obliterates a state or small country.
Those are the ones we know about. If you think about the problem, it really is a very difficult one to solve. We're attempting to find and track tiny objects that could be anywhere in an absolutely massive volume of space using almost entirely ground based equipment that is hobbled by competing demands, atmospheric distortion and a very inconveniently nearby star that halves the observation time and makes it really hard to find objects on that side of our orbit. For all the fancy animated maps of the many asteroids we have located there are likely still a very large number of other asteroids we don't know about yet and may not find out about until after the fact.
I don't see how making and reviewing notes is that different from making and reviewing cards. The more important aspect of using a system like Anki is leveraging the Ebbinghaus forgetting curve. Maybe if you already have the habit of making, organizing and reviewing notes you don't need a system on top of it like Anki?