10 days ago(+1)
Focusing on upgrading salary early on, though not neglecting detect, then just slowly clearing out pretty much everything on the map. A lot of it is just using logic to figure out what is guaranteed not an undead. Getting detect to at least 3 can help with most cases, but detect 4 will help out near the end. Even detect 1 can get you pretty far. I tried to maximize the resources that show up, getting 2 health off of an undead with bullets will allow the next melee hit to take it out. I leveled up survival to get the campfire upgrade to allow more heals.
In the end, I did have to pass up some undead since there the one empty spot that would score them was blocked off and I didn't want to risk taking health or wasting bullets. Reaching the town doubles the score, so I actually got about 15213. Going through the map as thorough as possible did take me a few hours.