Blake,
You don't want the pump to run dry for more than 30 seconds...
If I understand correctly, with the handle pointed up and the word "off" pointed down the pump will not prime.. if so, then we have two possibilities..
1. The main drain is plugged, either on purpose because it was leaking or plugged with debris.
2. Your pump has a suction side air leak and can't make enough vacuum to suck the water up to the pump.
My first step would be to take off the pump lid, inspect the gasket and lube it with "pool lube" and reinstall it. Then turn the pump on using only the skimmer and then switch to the 50/50 position. Use a garden hose and run water over the pump lid and intake pipes and see if the basket fills with water. If the pump runs ok when you use the garden hose, then you have a suction side air leak. The external water helps seal the leak.
To see if the main drain is plugged you could take the valve apart and stick a garden hose up into the top pipe and use a rag to prevent as much water coming down as possible. With the hose on full blast see if you see any indication of water coming out of the main drain...
Having said all that.. Main Drains are not really needed. I have two rent houses and neither of them have operational main drains, and the pools are just fine. If your plan is to sweep debris into the main drain in place of a vacuum, that will just not work. Main drains just do not have enough suction to make that plan work. In my opinion, if the Main Drain is working great.. if not, it might not be worth the effort to fix it compared to the limited benefits of having it working.
Your call...
Thanks,
Jim R.