Your post is incorrect because (inter alia) you are assuming that those with a mutation will only interbreed with those without a mutation. That has already been discussed. If there is close interbreeding other mutations will destroy the individuals interbreeding with close relatives. This is a very well established fact in genetics and explained in several posts already.
No. Your post talked about the spread of a single mutation. You were wrong in your math.
Why are you now trying to bring up other mutations?