First of all you shall never use that pennzoil oil,is the worst oil brand out there.
I don't know what kind of oil treatment you went with,but with the issues this engine came with i'll steer away from any "oil treatment".
If you have the $$$$ go have the engine rebuilt,ask your self if some one at this time will take your Vx with the blowed engine.
Personally,when is time for oil change what i do is this :
1 Unloose the oil pan plug a bit.
2 Run the engine for 5 minutes to get the oil soft enough to flow throughtout.
3 Get the oil pan plug off & let the oil run completly,i mean completly by allowing the oil to pour out for about 30 minutes.
4 Put back the oil pan plug but not tightening it.
5 Pour two quarts of new oil into the engine & run the engine for 10 minutes.
6 Have the oil pan plug off again & you'll be suprised how much old black oil would get outter the engine with this single step.
7 Screw back the oil pan tight
8 Add your 4 1/2 quarts of mobil 1 oil of your choice.
You need no oil treatment more then just two extra quarts of oil to get all that old remaining oil outter the engine.
You new oil you remaing cleaner than the average for a longer time.
I'm very sorry you going thru this situation.
My advice : Get your engine rebuilt.
PS: there's a use engine on ebay for $ 2000 with about 70K