You can't be both a Christian and a Skeptic. I'm not sure if this is a language thing or what, but those two things are contradictory.
Anyway - I wouldn't bother doing anything. In truth, I would avoid performing around him at all, and make a point of it. "I'd love to show you folks some cool stuff, but this individual prefers to disrupt any performance I do."
You are going into this with a challenge state of mind - the heckler always wins in that case. The absolute best you can get, in this scenario, is "Huh. I'm not sure how you did that." You still lose in that situation. Better to avoid it all together and preserve the mystery.