Hopefully now if you attach the mityvac directly to the shutoff valve with the car running it will shut off (without sucking in oil). If so, you just need to fix the vac leaks. First, test the ignition switch vac circuit by temporarily plugging all the aux vac lines (every small vac line except the line to the ignition switch and the line from the ignition switch to the shutoff valve), then see if the car turns off properly.

If the car then shuts off ok, then the leak is in your aux vac lines (lines to the hvac components and vac powered locks). Untill you find the leaks you could disconnect the vac powered locking system temporarily (if it is completely non-functional). I'd also suggest replacing any worn out, leaky vac check valves.