This is an old trick to "warm" the battery up before attempting a start. The battery has some resistance so drawing current through it to the headlamps creates heat and warms it up - makes it more efficient and able to provide more current. I'd say your battery is getting ready to go. As for the deposit under the oil filler lid, sounds like some moisture got in your crankcase and has been boiled off by hot operating temperatures. Check it frequently to see it it comes back after the oil change.