I remember reading about this problem a few months ago.
1. The oil filter filling up with sludge is not a filter problem. It is a symptom of a bigger problem. If there is sludge in the filter, then there is sludge elsewhere in the engine. Using a filter with greater capacity is a step in the right direction, but this may not fix the issue.
2. Low oil pressure can be the result of:
a) false readings from a bad or intermittent oil pressure sensor.
b) false readings from a plugged screen under the oil pressure sensor.
c) stuck or intermittently sticking oil pump pressure regulator.
d) leaking O-Ring on the oil pickup tube.
e) stuck or intermittently sticking AFM pressure regulator valve.
f) stuck or intermittently sticking oil pump pressure regulator valve.
g) worn oil pump.
3. I have captured some relevant liking relating to fixes:
a) Oil pickup tube O-ring and stuck oil pump pressure regulator.
Stuck oil pump regulator valve or pickup tube O-ring
b) False oil pressure readings
False oil pressure readings due to bad oil pressure sensor or screen below it
c) TSB to address oil consumption
AFM oil shield TSB
4. Since you have seen sludge in the filter, there is a likelihood cylinder #1 or #7 has excess blow by and the oil filter does not have enough capacity to go the full OCI per the basic OLM used in 2009. The TSB should address this for certain engines.
5. Pulling a valve cover would confirm the presence of sludge and help you make a cleanup strategy.
Good luck.