Damsel in distress

Sure, the oil sender going bad can make it not start if the oil leaked out and the engine locked up.

So far, all I have seen is you say the fan belt turns. I have not seen once where you have verified the crankshaft pulley turns, unless I missed it. THAT is what you are looking for. It is very easy to turn the fan belt without turning the crankshaft pulley. Especially if the belt is old and glazed. It will slip easily. If you can verify the crankshaft pulley turns and will turn a FULL 360 degrees without issue, then I think the engine may be ok.