I do agree with your first point, and it would basically be a continuation of the status quo, which seems like a pretty reasonable compromise between allowing people to profit from their work without stifling the creativity of others and criminalizing harmless behavior that is going to keep happening anyway.

My rebuttal to your second point is to acknowledge that you have part of a point, but also to draw a comparison between the futility of policing digital sharing and the futility of policing fanwork. Since we're (sortof) making a 'in a perfect world' wishlist, I think we can do better than fall into the same traps that current law/lawmakers/our assorted predecessors fell into, criminalizing behavior that is entirely or mostly harmless and where enforcement has minimal benefits.

With your other examples, I think that there is a case to be made on both sides with regards to the dangers vs the benefits from enforcement. But with those cases, I can more clearly see the arguments that enforcement has benefits that are worth the difficulty (depending on how damaging you think pot, gambling, and car accidents are). So I could see where a person would argue that noncommercial fanwork is severely enough damaging to the creator/rights holder to make enforcement worth it, but I personally don't see it as such and would have a very hard time believing such arguments without strong proof. Car accidents where someone is not wearing a seatbelt, on the other hand, has pretty demonstrable damages.

(I'm not really going to get into pot or gambling, because I think ath this point, the arguments for and against pot criminalization are well-established, and starting to weight every-so-slightly toward decriminalization, and I personally find gambling distasteful and boring and don't have the energy to read up on the damages associated with gambling or the benefits associated with enforcement of anti-gambling laws.)