I believe so, and in general so do the various state statutes.
If I do have that right then the number of hits is immaterial, since the end result is the same.
I don't agree. If someone threatens you with a deadly weapon, such as a hammer, then shooting him is certainly justified. But once the man is down with bullets in him he's no longer a threat. There's a difference between using deadly force to defend yourself and killing a man in the process, and killing him out of anger even though he's no longer a threat. It's not clear to me from this source whether or not the former or the latter happened.
There aren't varying degrees of "deadness", dead is dead whether from one shot or eleven.
No, but there are varying degrees of being wounded. There's a big difference between being shot once or twice and being shot 11 times, especially if it turns out that those 5 shots in the back are 5 gun discharges, not 5 shotgun pellets from the same discharge. People often survive being shot once or twice. The point of defending oneself with deadly force is to keep from getting killed, not to kill someone. If you kill them in the process of defending yourself, O.K. If you kill after your life is clearly no longer in danger, then that's murder.
I'll accept "heat of the moment". You pick up your gun and you keep shooting until the man's down. I realize that it's not a TV show. But I need to know more about the 5 shots in the back.