You inventory is just "over" your charm window. Move your charm window away from the inventory and you should be able to drag charms into it. This isn't a bug.
Anyway... BF without an exit? Are you sure you haven't just missed a spot? Somtimes it's a bit harder to find. Like last time when I searched I couldn't find it, it turned out to be on the last tiny part of the map I hadn't uncovered yet...
Also, to answer your other question: The more powerful you are, the less experience you get from monsters. If you're TOO powerful, you won't get experience from small monsters anymore. You have to find harder monsters if you want experience.
Tovi 