Of course you should be able to defend yourself, and I can understand people thinking reasonable force laws are a little on the restrictive side. Shooting someone, (or chasing them down for that matter) as they leave the scene is not self defence.
You're right though, this is getting horrendously off topic and nobody is going to change their minds. I'm just going to stop here.
Yeah, good measure for self defence is eye-to-eye, which is basically what we go through in the army a lot. (Special if you are on guard duty) By law, self-defence is needed when a person shows such aggresion that you can't talk your way out of it/leave the scene before it boils up.
By that, if someone hits you - you're allowed to hit back.
Now what is not allowed there is if someone hits you and you take up a knife and stabs him. That is against the law again, since you're overusing the force needed. So say he have a bat or knife, then you are free to defend with the same coin - you see something you can pick up and use, you are then ALLOWED to use it - because of your life is being in danger.
This also applies to if someone is getting attacked by a manman with a knife, then to save that person you are allowed to use any force up to his point of attacking. I.e everything up to knife.
Take up a gun and you will be charged for it, again it goes against the protocol for the force needed for the situation.
I don't think I need to explain the gun vs gun, you get the deal.
This is self-defence law used in Norway in a escalating form, but if someone is stabbing another person 30 meter away and you have no chance to run towards that person, while you carry a weapon. It does say what you will choose to do.
So it is a hard theme, what is overuse of self defence, what rules should apply for certain force. What is in the greyarea - for me I think it's more about how critical situation that other person or me are in, then escalate the force thereafter.
But I believe best defence is when you can de-escalte the whole situation and just calm down the whole situation.