More times than not IF you get any coolant out of the drain you are lucky. Try pulling the petcock completely out then run a piece of clothes hanger into the hole to break up the crud that's blocking it. You don't need the engine running to drain the block.

Yes a leaking water pump indicates the need for replacement.

The oil will not squirt into the valve cover. On a low pressure 216 the feed line is quite small. Eventually the rocker shafts will get full and you'll have some overflow but I've never seen one do what I'd call squirt.

If you have a bypass filter just start the engine without the element in the housing and watch to see if oil enters the side fitting and exits the bottom. If it does you're gold. The feed line will connect at the pressure gauge fitting and the drain line will connect at the distributor valve (on my '38 216 anyway, don't know if a '53 still has that or just a port in the block).

I don't know how you'd tell if it's been drilled for pressure from the outside, I've never done one.

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