"more than 90% of days from October 2011 until today have been bad days."

ATOS are only interested in the remaining 10% of "good days". Unfortunately it's that very 10% which renders you ineligible. Black or white: can walk or can't walk. There are no shades of grey where illness is concerned for these tests. That's the way they are composed. Bit like a multiple choice ..with only two answers!
Fortunately there is an appeal process, where a real human being assesses the evidence - I believe that around 40% of cases taken to appeal, win. Though they are slow, if the case is won, monies will be backdated.