I think the issue is more that in cases where the intruder is alert, there isn't time to make a critical analysis of whether they are likely to cause you or your family harm. There isn't the option to use half measures if the intruder has a deadly weapon and is willing to use it, and you can't tell from first glance if that's the case.

Sure, but why does uncertainty morally, automatically, sentence someone to death? Suppose I return to my car after I get out of a movie, and I see a stranger in the front seat who stands and walks toward me as I approach my vehicle. I know he accessed my property without permission and I have no idea what his intentions are or if he has a weapon, and he's coming toward me so there's no time for a critical analysis. Am I justified in shooting him dead on the spot because of my uncertainty?

Tasers aren't common, aren't legal in all places, and from what I recall aren't foolproof.

All of which is moot in my hypothetical scenario, in which I said "suppose for the sake of argument you had a highly effective non-deadly option." I freely grant that this scenario will not always apply, but I'm attempting to pry deeper into the OP's logic -- is lethal force automatically justified in every case, or is it simply the most practical option given a particular set of legal, circumstantial, and technological constraints?

If there was a surefire means of incapacitation, that would make more sense than lethal force to me.

I think that's the amended conclusion I was hinting at -- the justifiable goal is to ensure safety through incapacitation, and it just so happens that some of the most practical ways we currently have to incapacitate someone have a good chance of killing them. However, that is/will not always be the case, so a blanket moral justification is flawed.