In the middle game how many positions does a GM analyze before making a move? What are typical limits of top players?
Of course this depends on the position at hand, but generally speaking...
I am not a GM, but 100 positions (not moves) seems highly exaggerated, though this might depend on your definition of "position" and "analyze".
If you really mean unique (and not only slightly different) positions, and if you mean by analyze, the full process of evaluating the position, I would guess that the number is between 0 and 3 or so.
Only rarely you would want to calculate forced line and would have to analyze a position in the future anyway. Most decision making is based on well known plans, that follow from the current position on the board.
Nobody is safe to answer this question unless he or she is a GM. You definitely need to search an answer in chess games. You can analyse by yourself or by using chess engines or you can easily find many videos on the internet. One of my favourites is the game between Vladimir Kramnik and Garry Kasparov when Kasparov sacrificed his Queen on move 12! It reveals in a great way how a GM can "create" the future through many moves before.