Hmm, is it just me or does it sound like Alan was manipulated into making a hex that was stronger than intended? To me it sounds like Alan wanted something that would make Douglas weaker but not kill him. While the other guy wanted to kill Douglas to become #1. The curse going back was something that forced the other guy to kidnap the daughter to save Alan. While Alan at this point seems like he is kind of out of his mind.
I 100% think that Alan was manipulated and effectively brainwashed by what he though was his best friend.