Upvote:4
There really isn't a good alternative. You could try to go further south via A39, A7 and/or A44 but it's substantially longer and has pretty much the same traffic challenges (if not worse). High speed train (ICE) would be significantly faster and more predictable, if that's an option. It's about 4.5 hours. And they sell beer on the train :-)
As said in the comments, real time traffic monitoring with google maps or equivalent is your best bet here.