just make sure that if you do have to shoot him you kill him, but as for any other physical violence ur literally better of shooting him and killing him in terms of legality and repercussion.
Wrong!
That's terrible advice. You DO NOT have any justification to kill someone. You only have justification to use deadly force to stop a threat of serious bodily harm or a forcible felony. If the threat stops, then - legally - you have to stop using deadly force. Anything other than that could land you in jail for a very long time.
Killing someone is never better than injuring them as long as the threat is eliminated. Let's say you somehow made a mistake in your belief that using DF was legal in a certain situation you were involved in. If you kill the person then you will now be charged with murder. If they are just injured then it would only be battery or similar.