For your issue with inserting a sheet list table. Make sure you're in paper space when you attempt to do this, it will not work in model space. Number of sheets should not be an issue; A couple years ago did a sheet list table for a set of drawing that had 535 drawings in it without any issues.
I've been having this exact same problem with adding sheets to a sheet set using ACAD 2016. We have multiple people working with the same sheet set and the only solution we have found is to have everyone close the sheet set. Then I will close my copy of the sheet set and reopen it. This usually works.
It seems like there is a lock being put on the sheet set as if someone else is currently editing it. In our case no one is editing it, they just have it open.
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