Issue 1: Adobe Reader is really buggy in this version. It also closes if you do a long press to get to the next section. The bugs have been reported in a German forum, hopefully Pocketbook will release an update next week.
Issue 2: If you open a book with FB Reader this gets written into handlers.cfg, a configuration file that stores the reader for each file. You should be able to change to Adobe by selecting "open with" after long press on a book in the library.
Issue 3: Have you tried setting a bookmark as a workaround? As an alternative software, I can recommend Coolreader. Everything works fine with that.
https://www.mobileread.com/forums/sho...d.php?t=256917