I really like that routine Blank Night by John Archer. It's perfect for a corporate gig if you want to do a cabaret spot after a meal, or for a stage magic spot. John has released this item commercially, so you are 100% OK to perform it just as John teaches. He charges a fee to magicians for just this service when you buy it from him. So from an ethical point of view you are 100% fine to perform it just as he teaches.

I think an issue only arises when a performer tries to add an effect together with it's original presentation style even though that doesn't suit his or her persona or the rest of the material in the act/set it will be presented within. It sounds to me that you were attracted to it because it fits with your clients and your style ( Excluding the 'sex' bit) so all is good for you to use it.

Have you watched Johns performance on Penn and Teller, then realised that you have your own method for the mechanics of the routine? If so, I think you should probably buy a copy of Blank Night from John, so that you have compensated him for the idea and what you have learn't from him. That make sense?
Dominic