Arcing from the rotor to the cap is normal. The rotor does not touch the cap terminals as it rotates, so the spark jumps the gap. This arcing slowly wears the contacts down and this is why over time it needs to be replaced. It could be a bad coil. The wd-40 might not have been the best to use for cleaning, there are some sensitive parts in there. I would clean everything out with some brake parts cleaner and reassemble it, then try starting it again. As to the humming you are hearing, that would most likely be the IAC or Idle Air Control valve on the rear or the intake manifold. It is a frequency modulated soleniod; and on failed starts it will sometimes hum like that because it's trying to adjust air flow to start the vehicle. If you turn the key off and then back on, it should go away.