i think your rad cap maybe bad, or not on right, aka hooked on both sides. the tank will rise and drop, but if you squeeze the upper hose and coolant blows into the res tank, the caps not tight or shot for sure.
the side rubber side gasket has nothing to do with coolant, its just sealing air from getting inside to outside.
check your oil. if the dip stick has any milky looking crap on it, change it asap.
if you just see clean new oil on the stick the oil is fine.