Oil pressure and oil level are unrelated other than no oil= no oil pressure.
Idling so low should be expected to set the low pressure light flickering. The low pressure is a result of the low idle not the other way around.
Unless your crankcase was overfilled you need to examine what is going INTO the oil; fuel from leaking injectors or coolant, coolant will turn the oil milky, fuel will simply dilute it compounding any low pressure condition.
Your surging idle is likely a vacuum leak or idle control valve fault.
Seafoam will do nothing for any of this.