I abandoned my playthrough back then, because the developer didn't fix reported (achievement-related) bugs, and judging by the posts on this game's Steam forum, these issues still persist. Anyway, a demo version of this game has been made available on Steam since your post - such magnificent timing. :D
Honestly, I don't understand this game's price cycle, going from initially 10 to 0 and now all the way up to 50 bucks. It's probably better to just play Mystic Quest Legend (aka Final Fantasy Mystic Quest) instead, since Jacob's Quest isn't much more than a recreation of that game.