1. Wraith Fever is a sickness. You can get it from rats in the bar basement.
2. It should be. Just there's not many chances to improve the relationship with him.
3. I will make some kind of guide (When I find some free time).
4. The most content is for now in shopkeeper relation. I'm planning to add other NPCs from Bareshade. Maybe Scar and Tank too. Who knows.
5. Love Potion can be used on Shopkeeper only. Used in fight should increase the attitude of the enemy you are fighting.