Okay, so this is a question based on a real life situation I was involved in.

I had a man with a knife run up on me during a road rage incident and try to forcibly gain access to my vehicle, presumably to attack me. I had no direction that I could flee in, because there was a line of cars in the left hand lane and one in front of me in the right hand lane. He was parked directly behind me when he exited his vehicle and ran at mine, and there was a curb I could not have driven over to my right. Thankfully he was unable to gain access by ripping at the door handle, so he just pounded on the glass for a moment before turning around and leaving.

Now, here's my question. I am in a stand your ground state with no duty to retreat. Had he gained access to the vehicle, in light of him having had a knife and making clear indications that he wished me harm both verbally and non-verbally, I believe that a rational person would conclude that I would have been within my rights to use deadly force to terminate his attempt to attack me with a deadly weapon,

Now, here's my question. Would I have been within my rights to use deadly force had he gained access to the vehicle by breaking the window or ripping the door open? Assuming I would have been within my rights to use deadly force, would the manner in which I apply deadly force change that determination? I was unarmed, so my only realistic way to fight back (he was larger than me and armed) would have been to back my car up and then proceed to ram him with it or run him over. If the events that day had played out differently as described in the question, would I be able to claim a justifiable homicide defense in this rather unusual self-defense situation?