I'm pretty sure UNH does own the tiebreaker with Me and PC so,
IF UNH GETS 3 PTS VS. MC:
SCENARIO 1
NU/BU SPLIT---NU 24 PTS
ME/PC SPLIT---ME 23 PTS
PC 22 PTS
UNH GETS THE #4 SEED
SCENARIO 2
NU SWEEPS BU---NU 26 PTS
ME SWEEPS PC---ME 25 PTS
PC 20 PTS
UNH GETS THE #5 SEED
SCENARIO 3
NU SWEEPS BU---26 PTS
ME/PC SPLIT---ME 23 PTS
NU 22 PTS
UNH GETS THE #4 SEED
SCENARIO 4
NU SPLIT---NU 24 PTS
ME SWEEPS PC---ME 25 PTS
PC 20 PTS
UNH GETS THE #5 SEED
I think I've done this correctly. Please correct me if I am wrong on this
In your scenario 3, you mean PC ends up with 22 points, not NU.
I think that your scenario 2 is the most likely, so not good having the Cats heading to Alfond.