Simon read with great interest your post. Most folk suffer some sort of illness throughout their life how we cope with it in or own ways is each persons choice. Soem folk turn to booze to ease the suffering. The down side is some of the ays choose really affects others we become so wrapped up in our own suffering we forget the impact our behaviour may have on our friends and families.
As for going to his house with a hammer Simon I would not condemn you for taking the boy scout approach "Be Prepared" drug dealers no matter how they may portray themselves are already outside the law and commiting another criminal act does not worry them. They have to rely on fear to ensure that they dont get any grief from other dealers or non payers. (This is not me making excuses for them)
Threatening families is an established tactic from these people. I have a similar experience from a local dealer who sold drugs to a younger more vulnerable family member. I eneded up with a an addition on the National police data base for my actions.
Would I do it again in a heart beat. The only mistake I made was not to hurt the little badly enough. It became uncomfortable for a while as all this dealers little friends decided to make my life awkward. I ended up being harrassed by roups of young neds until something drastic happened.
This forum is not the place for me to into details as far as I know the case is still open with the police. Suffice it to say the police know that I did it they know why I did it but the cannot prove I did it.
Watch your back mate these animals will try hit back in some way. Keep one eye open if they do come back you two options run or fight.
I cannot tell you what is the right course of action for you I will not presume to try and tell you what to do. I will wish you well and hope it all blows over.