My kid was driving our 2012 S ALL4, 84k miles, and said that as he was pulling into his street he lost normal braking and the pedal went stiff. I showed up and verified super stiff pedal even following the startup test where you pump the brakes a few times before starting. No change in pedal stiffness.

Not sure if what I did next has now caused the red oil warning light to come on or it's some other issue but I disconnected the vacuum hose that goes from the brake booster to the vacuum pump to see if I could feel any suction (none). Plugged everything back together and figured car would be ok to drive the few miles back to the house. During that short trip the low oil pressure light and the half power lights came on. It's throwing a P0012 code. Could the vacuum line disconnection cause this? Also checked the oil and it was about a quart low.

Initial thought was the brake booster check valve was reason for brake issue but after reading up a bit might the vacuum pump be causing both the low oil pressure and the brake problem?

Thanks in advance for any assistance.