So...
I managed to JB my kindle paperwhite 3!
I wanted to thank you people for your help especially to knc1 for the detailed steps

i got back to my 5.8.2 version and i managed to make librariansync work. not unfortunately ixtab CM which i like better.
uhhh couldnt make scrrensaver hacks work....gotta go ask why.
but Iam quite happy with the jailbreak, thank a lot!