You must put a padlock on your car, once you do that you claim it, otherwise anyone can take it once its off your base boundry, your car shows up and is safe when on your base, but once off base with no lock anyone can take and loot it, also, lock your house doors to stop others entering.
Next time you die play as a zombie, you have 15 mins before you die, once a zombie you can look for the large yellow plants on the map, eat it and return back to human, Also the plant fruits you can pick to eat to remove infection, the boss was infecting you, next too your HP and hydration you have an infection meter, it was filling up as the boss was firing at you, you lose half your loot when you turn into a zombie but choose to repawn as a human instead. when you're a zombie you can add mutated parts to your body and become a boss...haha
Send your NPC's out on missions to get feathers etc, the more you send them out the better loot they collect.
You should also work out daily with dunbell, you get xp multiplyer for it once per day, same as meditation and dancing it levels your charisma for more followers, more followers = more scavanger missions.
Sorry for the long post :D