The Kindle displaying the screen saver shortly after the jailbreak is not a bug, but a feature -- i.e. a part of how the jailbreak works.
At least, install usbnetwork and try to connect to your device before you claim that the jailbreak doesn't work.
Look at
https://wiki.mobileread.com/wiki/Kindle_Touch_Hacking for explanations.
(@all: yeah, blatant marketing of the Wiki page, I know. I still think it's useful ;-) )