Re: the screw/nail pop. Yes, even screws back out of lumber. What you're seeing is the compound being pushed away as the screw/nail backs out. Remove the lose cap, remove the screw and replace it with the next larger size screw. DO NOT OVER TIGHTEN THE SCREW. If you do it will most likely draw the wall board in and cause nearby screws/nails to push compound away, requiring more patching.
If you're dealing with a nail, drive it in a bit and place a screw next to it.

The crack caused by settling will most likely require frequent repairs until the settling is complete. Use a razor knife and cut a V shaped trench the length of the crack, 1/4" deep X 1/4" wide and fill it with vinyl repair compound.

What you have here is very common in cold areas. And this year, most everywhere is a cold area! The cold causes structural shifting and a crack above a door or window where there is a joint. For info on the solution, see Retaping Crack Above Window