Yet it will often result in the shooter not being charged.
Sorry, some common sense must be used here and many defensive shootings never progress to an arrest because all the pieces fell into place at the scene.
Don't get elaborate. Don't hypothesize. State only what they see and stick to having feared for your life and having acted to stop the threat. Beyond that is lawyer time. Saying nothing will GUARANTEE being guilty in the LEO's eyes first.
Nope. Only in the tiniest of tiny towns would this work. In every town and city of any size, all shootings will be investigated - not by the first cop called to the scene, but by detectives and professional investigators who will not be terribly impressed by what you volunteered at the scene (but who will certainly use it against you should it prove helpful to them).
Contrary to what you might think, I'm not suggesting never cooperating with the police nor never saying anything to them, only having a competent attorney with you when they do ask questions, so as to help you avoid making potentially contradictory or unintentionally self-incriminating remarks.