1950’s home - Step crack on front exterior (seems to have been “repaired”) - vetical crak below window, crack in ceiling and matching diagonal cracks over opening from LR to kitchen.
See diagram
Also, right read was “sealed” at some point - evidence of water intrusion in this rear area.
How could you its covered always love covered attics lol. Looks as if the floor is bowed a bit. Did you take a level to it? Did you take a level to all the floors and door frames? Did any doors stick? Could you see more light on side than the other? What was the sill like? Any broke boards attached to the sill? Any WDO damage to the sill? Any checking involved with the sill?
Recommending a structural engineer would imply that you feel the structural integrity of the building has been compromised. Based on the information you’ve posted, I don’t believe that to be the case.
With the frequent seismic activity in CA, these conditions wouldn’t be much of a concern.
Absent of earthquakes, I would be more inclined to recommend a geological evaluation in order to determine the cause of the movement.
In any case, if slight pressure were applied to the ceiling at the crack, and ceiling moved up and down, then the ceiling system has an attachment problem. It is possible that nails were used to hold lath up and they are now pulling out of the joist.