1) Which BF5-key did you find? There's a joker-key... The real one is in one of the rune-rooms.
Wasn't aware there were two. The one I got was in the chest at the end of the chain of keys. I may have gotten the other one as well, all I know is that when I enter the BF it says it's level 5.
4) The only arrows you can convert are Normal Arrows. If you are sure that the arrows are with your hero and he is leader, then I don't know what you're doing wrong. It worked for me.

Yeah, I'm sure. Maybe I need to try a different arrow choice. I chose Power Arrows because they were the strongest, but I could try Splitting Arrows. Maybe the Power Arrow conversion is broken. Oh well. Thanks for the reply.