XP Debt is totally irrelevant in FoV.
There is a non-plot dungeon in the pig pen in Mardaneus plaza, before I went in there at level 35, I had 100k experience debt, I not only cleared it, but gained an entire level's worth of XP.
There's also another non-plot dungeon in Mardaneus plaza near the funeral pyre.
Enemies respawn in this game, so there's no danger of running out of potential XP gains before you mind-read everyone.