Great advice above from Hellymedic. I speak as a champion faffer!!
My first Audax was a 200. I had already done a couple of 100 mile rides, so it was only a little further.
Since then I've done several 200s, 300s and further. Your proposed schedule of a 100 every weekend is quite a challenge (but then I have domestic obligations).
I am a naturally cautious person, and after building up gradually over 3 years, completed my first SR series this year, witrout too much difficulty......
Take it steady, learn as you go, and there is nothing you cannot achieve.
Good luck
Lycra Man