Perhaps there is no linkjail folder due to interference during the jailbreak install from files or folders that you COPIED from the old kindle DX to the DXG.
Get rid of the files you copied from the old kindle, then try uninstalling the hacks, do factory restore from the settings menu, and then reinstall the hacks.
One of these days I am going to read the source code for the kindle hacks when I get more time, so I have to use less educated guesses, and can answer from a solid experiential knowledge base.
AFAIK, only NiLuJe fully understands his hacks.
I long for the old days of simple C variable names from vintage K&R. I have yet to explore the code and coding conventions of the kindle hack source code...
So, for now, just hopefully helpful "guessing" from me. Perhaps NiLuJe (or others) can be of more useful assistance to you...