I'm disagreeing with your statement that "you're only allowed to use deadly force in proportional response," not with whether this case is being prosecuted rightly or not.
Mate, read that link I put in there. I can tell you, from experience, that if you shoot at someone stealing your property in Texas, where that penal code I posted is from, that exact portion of the statute is going to be used and you will not be convicted. It really is "anyone could have a gun or knife." At least Texas has it so just theft has to be during the nighttime, so I guess that's something.
You'll also get similar worded statutes in many other states in the US, several of which, stating this again, where I've had the misfortune of having to research those laws. And that "reasonable belief" part about exposing yourself to risk of serious bodily injury or death? I have seen it applied to people who are simply physically larger than you. Proportional response is a moot concept.
Are you sure that you understood that right? In every study I've helped out with, and when I'm dealing with patients, rule #1 is that the participant/patient has access to their information produced from the procedures and gets counseled by a doctor involved in the process if anything is found. There's a neuroscience professor who famously recorded his own experience in the textbook he wrote, where he participated in an MRI study because his insurance wouldn't approve an MRI. The tumor was found in the study, passed over to his healthcare team, and they were able to use it to get the surgery approved.