Will not start after running very low on motor oil

Most likely spun a bearing. Charge the battery , just as a precaution , so when you go to crank it , you know it's not slow/ or 1/4 turn , because of a marginal battery. Only other easy (relatively speaking), would be to remove the spark plugs and then try to spin the engine, possible blown head gasket and not spun bearings , but I think unlikely. IF it is headgasket leaking ,it could be 'hydro-locked' , but I doubt it would turn as much as you describe each time you try. Usually , on engines I've seen hydro-locked , you can watch the crank pulley turn maybe 1/2 inch , then remove the plugs and it 'releases' it. Good luck.