I've hesitated to post about #2 and 3 because I can't figure out any sort of pattern on them. I'll keep an eye out, but for now, I just gotta leave it as "thing that happens, sometimes."
Sorry, I know that's frustrating and next to impossible to work with :-/
For the search results, perhaps, could it be changed so that clicking the thread-title does as it does elsewhere (leads to last-read), while clicking the message body preview takes you to the exact shown spot?
Dunno, maybe I'm just the only one who searches for threads rather than specific posts :)