That's a lot of what ifs.
Theres only 1 question to ask when debating if you should use deadly force.
"Is this worth dying or spending my life in jail for."
You will have a prosecution team that gets paid to try and figure out how you screwed up, and a jury that has all the free room and board they want to second guess your decision.
Were not police officers. If the fear of death or great bodily harm is present, then we need to be prepared for the potential consequences to adding a gun to.the situation.