I would have used a simple
. If he decided to try and attack me with the hammer, I'd take it from him and break his right collar bone, disabling his attack arm and making the choke a lot more painful.
I'll run if there's a gun, but I'll probably intervene for anything less.
If anyone is interested in being prepared for a real life dangerous physical situation like this, I strongly recommend taking a martial art like krav maga.
Oddly enough, Ch'i was jumped the other night by some punk that wanted to take his wallet. Ch'i ended up using the guy to practice moves on, things like elbowing the back of the attacker's head and jump reverse side kicks.