Yes, creating a tempo map that matches an existing audio is exactly what I wanted to do. I'm going to try your solution but I'm wondering why it is so complicated: in Pro Tools First, you just have to identify the first measure, the last measure, the middle measure, the middle of the middle, etc. and you are done after 3 to 5 identifications.
And regarding audio snap, I just don't understand how it works, even after having learned hours and hours from tutos on youtube.