Taken from the walkthrough
http://www.aldorlea.org/officialsite/phpBB3/viewtopic.php?f=65&t=1636Side quest 16- restore treasure chest (Q 71)
...Go down into the bottom left room and Zahor will give you a scroll that gives you persuasion + 10,...
...Which gives a total of persuasion: 45,... If you have 35 Persuasion Points, then you probably missed the +10 scroll, because maximum for LF1 seems to be 45, at least according to the walkthrough.
I don't remember if there is any other way how to boost your Persuasion Points in LF1, though, it has been more than two years since I've played LF1 for the last time. And unfortunately I cannot simply check how much Persuasion Points I have in my final save, because there's no way how to display stats like this (unlike from kills, hits and so on).