1991 Cherokee Laredo / 4.0L stock / 132,000 miles

My fellow Jeepians, I have a minor problem that is perplexing me. My Cherokee runs like a top, however, it leaks (nothing new to Jeeps, I know. When I first bought it about a year ago, it didn't leak too bad....a drop here and there....then I had the oil changed......it began spraying out of what I suspect is the rear main. Tires Plus forgot to put a gasket on the drain plug. Problem fixed.......not. When I was cleanning the engine to look for leaks, I accidentally broke the front vacuum valve on the valve cover. I looked everywhere for a replacement and failed. I had to drive it one day, and was white knuckling it to pull n pay. When I got there.....I realized it wasn't leaking. I thought that I had run it bone dry, but it was full of oil when I checked the dippy.
I bought a replacement and put it on in the parking lot and drove it home, and it leaked a trail of oil all the way home. I played around and found that it I left the broken vacuum valve on = no leak, pressure around 60. New vacuum vlave on = major leak, pressure almost at 80.
Not being mechanically inclined, I've opted to leave it broken, and have driven over 5,000 miles with no issues, good pressure and no leaks.
So I figure that, for whatever reason, the broken valve created a "vent" for the oil pressure. I have changed the oil three times in 5,000 miles to stay safe, and the oil level stays normal, so oil overload is not the issue.
I dunno what the issue is, so any help is appreciated. Am I harming anything by leaving that vacuum neck broken and open?

Thanks

Hoolz

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