I have contacted Samsung support about reversing the update, and they told me it is absolutely impossible. So I assume that there is no way of doing this without rooting the Tab.
(Samsung of course didn't mention the "R-word"...
I'm not even sure you can reverse after rooting. I have found documentation on how to change the UI back to a tablet UI (within JB) which should solve most of the problems. But I have not found anything yet on installing an older version. (I am however completely new at this. I just started looking into the more technical aspects of Android after the forced update a few days ago.)
But I do find it ironic that after decades of Microsoft bashing I have to admit that at least with Windows it has always been relatively easy to reverse an update or install an older version of the OS.