..In the ASM2 Spiderman is able to outreact lightning strikes from Electro by stopping people from handling an about to be electrified staircase railing....so I am wondering just fast are his reflexes? Not lightspeed, but supersonic speed + some?
This isn't quite the same as what you're saying, but here he does manage to knock someone out of the way of an electrical blast, after the blast was fired. (Read right to left)
And he's been able to dodge lightning several times throughout his career:
In the second scan of this batch, he's even doing so without his spider sense.