Ok, here's where I draw the line.
I decided when I started carrying, that I don't draw unless I'm going to shoot, and I don't shoot unless I am pretty sure that this is for real. If I get a busted tooth, a black eye, a broken nose, something like that, BUT: I don't think that it's going to go any further than that, I WALK AWAY. I don't pull out my pepper spray, I don't put him in an arm lock, I don't push him back. I don't progressively escalate force.
Now, if the same guy hits me, and it looks like he is going to hit me again, and he looks mad enough that I don't know when he is going to stop, the deadly force switch comes on. He might back off immediately when he sees the gun, and if I realize it in time, I will turn the deadly force switch back off.
If a total stranger approaches me, and is trying to hit me or DOES hit me, and I am unable to create distance between me and him, and he will not respond to commands to back off, the deadly force switch goes on. Now, any of a hundred things can happen at this point. He could break into giggles and say; "Just deleted -- <Sam> with you man," and walk away. But if he KEEPS APPROACHING AS HE DOES IT, the deadly force switch doesn't turn off.
I THINK, the best way to do this is to keep it simple. Don't complicate yourself with checklists of what to do in varying levels of defense. It's hard enough to train to react with the bare minimum of rules. (Not to mention how hard it is to defend yourself AFTER the fact even when it's simple.) Don't keep 'what iffing' yourself.
As black and white as we can make it, is to quote the law. In MY STATE, a person is allowed to use deadly force to prevent a violent felony, serious bodily injury, or death. If a person enters my home, either by violence or by stealth, with the intent to commit a felony, deadly force is allowed. I am not required to retreat, but I absolutely will if I can.
Where you, (and all of the rest of us,) have to make a decision, is whether or not YOUR perception of what is reasonable matches the rest of society. There are gun guys who can convince them selves that they need to shoot someone even if pretty much everyone else on this board tells them no. These guys will probably have a hard time convincing a D.A. and jury that they needed to use deadly force. We say; "It is better to be judged by twelve than carried by six." but that doesn't mean you WANT to go to trial for murder. It only means it's better than being dead.
If you are asking us to tell YOU what YOU should do in a hypothetical situation that hasn't happened, where YOU will be there and WE WON'T, it's impossible. You can't tell the jury; "But the guys on THR told me it was ok to shoot between the second and third punches." It will never work like that for any situation in the world.