I agree that the weed fight isn't worth fighting, but it's still federally illegal. If we're going to have laws that we choose to not enforce, those laws need to go away. Otherwise, they rear up in bizarre combinations of places, like "if you have an MMJ card you can't buy a gun or have a CCW because the MMJ card is defacto proof that you illegally use".
As to chances of getting caught on NFA stuff, also, agree, but it's still an unconstitutional law that has been dodged over and over instead of being properly heard in court. I'm sure we all disregard some laws (speeding, tires sticking out, taillight height, reporting income from a garage sale....) from time to time that have lesser consequences, it's a matter of your comfort level. Philosophically, I think it's bad law that needs to be overturned, regardless of how easy it is to ignore it, or how infrequently or unevenly it's enforced. Keeping it around is just waiting for a round of bad leadership to decide it's suddenly priority number one. A bad law that doesn't affect you, is still a bad law. And with the cyclic nature of politics, don't give power to a leader you agree with, that you'd deny to one you don't agree with.