Hi and welcome,
Regarding the oil pressure warning lamp, you did mention that you gave it a good wash, I believe that water sometimes gets into the switch and can make it come on or light dim.
With the level, double check it again I think.
Use the same spot of ground, make sure the bike is at the same level and the engine is cold, make a note of the level in the sight glass. do a few hundred miles and recheck with it cold again.
As Ian says it must be going somewhere, not spraying out of a faulty pressure switch by any chance??
Have a look in the air box as well, should be clean.
Good luck.
