Living in denslier populated areas makes you use less energy, because your commute is shorter, you need less energy to heat, you are sharing all the infrastructure with more people, so footprint/person decreases.

I don't think I am very far along. If you have a lifestyle like I do, you get most of the benefits almost for free. Improving upon that is very hard.

On the other hand, I think someone living in a (first world) village, could be way more conscious about these things than I am and would still have a hard time to come close, just because he or she is sharing his house/car/roads/infrastructure with less people.