I like the idea of a voicemail, although it would put you back to waiting again, which is hard.
The voicemail sounds good. I might go for something like "It'd be good to discuss this just so I completely understand what I'm signing" or something like that? Give him a chance to explain the rationale to you without suggesting there might be alternatives.....
Definitely wait til Monday and have a fabulous weekend not thinking about any of this!
