4.8is strange oil pressure / oil level behaviour

[spadge]

Since yesterday evening I have the following issue:
after driving some kilometers (about 10km) and engine gets warm (outside temp is below 0°C / 32°F) I will get the "STOP! Oil pressure" warning if the engine gets down to idle rev.
Checked the CCV - both membrane are fine, passenger side membrane is a little bit polluted by the white oil slime but not cracked (ordered a new one today and will replace the passender side one). As soon as the engine gets to higher revs, the warning will disappear. Engine sounds good at idle.
After turning the engine off I will get the "check oil level" warning. Dip Stick was kind of dry directly after turning the engine off.

Checked oil level this morning: everything was fine, after about 10km same procedure as yesterday evening... Turned off: "check oil level", dip stick is nearly dry.

Since about 2 weeks - after engine gets warmer (>10km) - it kind of "rattles" and "shakes". According to the error codes the ignition coil on cylinder 5 was broken, replaced it by a new BOSCH one. Other fault code stored was "vanos inlet" on bank 1 & 2, which sounds like the vanos solenoids to me (clogged maybe?).
Maybe this has to do something with the oil pressure thing I got since yesterday as the vanos solenoids are controlling the oil pressure for the vanos itself?

Other assumption: oil "non-return valves" - postion 8 at RealOEM.com - Online BMW Parts Catalog

Any suggestions? Maybe someone of you guys already had this issues?

Oil pump shouldn't be the issue in my opinion because the oil level is too low after engine gets warm, so it seems to work correctly, right?
Ordered a new oil pressure sensor today, but I don't think that it's broken...

It's a 08/2006 4.8is (N62) and has about 155.000km