2005 1.8t Passat

So, my Passat has been running strong since we bought it
in March. Had a check engine light when we got it,
Advance Auto said something about sensors. Well, here
we are mid-July on a road trip and the oil light beeps,
flashes, and says Oil Pressure STOP MOTOR. So, we let it
breathe and it did fine. On our way home, after about 400
miles, it came on again. My husband changed the oil
before we left, put in a quart of Lucas and 5 quarts of
5W30. He had only put the quart of Lucas and 4 quarts of
oil before his father jumped in and said "add the last
quart, because you have to account for the oil filter." My
husband disagreed, but did it anyways. So, checking the
dip stick, we have too much oil. As long as we keep the
car at 3000 RPM and under, the light doesn't come on. Is
this a sensor issue or too much oil causing my pressure
light to go crazy? I've heard a lot of different things that it
could be, but every situation is different. We haven't had a
chance to go have the oil pressure gauged and I'm hoping
a mechanic can just give me some answers on what it
COULD be.