Oh thanks, @Blogospherianman, Neither was I aware of the "Meter/Key" window's functionality nor its existence but your suggestion totally saved my project and day:
I shrunk the first bar down to a signature of 1/32 to cover my anacrusis and the rest of my composition got a 2/8 signature assigned (because, well, to fit the results of Cakewalk's automatic tempo map. Just too lazy to transform it into 2/4 or something ?)
Anyways, I wanna thank you all for your nice support, had no idea this forum was filled with such a number positive people ^^