Oil pressure in 99 Contour

I have a 99 Contour (4 cyl) and recently (last couple days) started losing oil pressure when making sharp right turns or sometimes braking hard. I recently took a new job where I drive a ton of miles and (stupidly) got way
behind on my oil change; I went to check the oil level and the dipstick handle broke off in my hand!?!? I was leery of adding oil since I can't check the level, but I put about half a quart in and the oil pressure idiot light didn't go on for a while, then started up again. I put in the other half quart with the same result. I dunno if just dirty old oil would cause this problem - I mean, yeah it would if it was low, but only when turning right or braking? That's what weirds me out. I also noticed a threaded hole in the bottom of the crankcase (not the drainplug) with nothing in it. Did I lose a bolt somewhere? Oil pump problem? Sump? Cracked head (please no)? Is that hole supposed to be there? It doesn't look right, but I'm afraid to screw a bolt into it without knowing. I'm taking it for service to get the dipstick out and having them change the oil while they're in there (no one, including me, wants to do it without being able to check the level after). I'll have them look it over but I'd like some other input before I hear any scare stories from a mechanic who spots my ignorance with dollar signs in his eyes.
Any ideas? All are appreciated.
If I had the extra loot I'd invest in a gauge. Not knowing what's happening when the idiot light isn't on is driving me nuts. Imagine if your temperature gauge were replaced by a light that came on when the engine was about to seize up.
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Jesse wrote:

This whole story sounds like a put-on but, light coming on during a turn or braking IS an indication of low fluid. Many cars DO rely on nothing more than an idiot light to tell the operator the engine's overheating, some going so far as to have the same single idiot light for low oil pressure AND/OR high coolant temperature. You can buy a mechanical OP gauge for less than $10.
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