He is harmless currently because you have not started the ritual progress yet. You might run into Sam while he is walking around, but do not panic. The buildings that are lit up are your main objective buildings. Since Sam has been summoned, head back down the path to the town, (which will now be lit up. Burn them if you can in Normal, otherwise for Hard and Nightmare I would recommend trying to dodge them until it becomes impossible to do so. The ghosts can go through walls, and will become very annoying. From here on you will be using your flashlight to burn away the demons on this map, which are ghosts. Once you are in the church and step into the Pentagram in it, Sam will be summoned. (There are a couple entrances, this is the one you will mainly use). When you walk to the right of the saloon building leading to the back you will find a pathway marked with cross gravestones. After this, walk outside, nothing has been summoned yet. The key should be the key for the Church. When you enter, walk towards the window and collect the key on the table. Walk up the stairs directly to the left, (you will hear footsteps), and walk into the bedroom that you hear the steps from. To really get the game going, walk into the building that you hear piano music coming from in The Saloon.
You do not need keys to unlock doors, so feel free to read papers, explore rooms, etc. (Feel free to explore, otherwise here is the game progress).
When you first spawn in, you are on dirt in front of the town. It is also very difficult, (it can be more than the other maps). This map is like a combination of all the maps, however the gameplay is very different. Note: New DEVOUR map The Town now available to play on March 25, 2022!