[AZKen]

The low compression has nothing to do with oil pressure. You may have blown head gasket or bad valves/springs and all that stuff. Don't run it too much until you figure it out. Check your oil for milky look.
The fact you have very low in 1-6, which are in the firing order sequence is a hint (165432). Their location is far apart. So possibly is not head gasket, bad piston, broken rings, I.E. cylinder related. It could have something to do with timing. Chain/gear slip, broken. To further my timing related suspicion, the two PSI's are WAY low but equal. Just guessing. What are the other 4 cylinders?
It could also just be a coincidence. Could be that they are at the ends of camshaft/crankshaft. Check the valve springs closer. Also could be valve seat, bent valve............
I don't know, just trying to start a brainstorm.