I would still do the same exact thing. Y'all can run around dialing numbers while a maniac tears his way into your castle, your belongings, and your wife if you want to; I'm showing him that there are easier targets to be had. In that situation, 99 times out of 100, he will turn and flee, never to be heard of again. Those are damn nice odds, and they're the ones I'd be going with.
On Scenerio #1, I'm not saying not to use lethal force. I am saying not to tip your hand until you must. Doing otherwise can open up a whole realm of possibilities. Yes, chances are he will leave. If he is intent on doing you harm, he will find a better time and place, when you are less prepared. If he is on drugs or drunk, he may very well continue the assault on your door anyway. If he is an enraged relative, or suicidal, he may continue the assault on your door. Someone who is assaulting your door with force is not behaving rationally, they are enraged. Showing them a firearm is not likely to suddenly make them rational. If anything it will escalate the rage.
If he breaks down your door and enters, you are justified in dropping him on the spot where I live. You will likely not even be taken in for questioning. You will loose your gun to the evidence locker until the case is closed. You will have to clean up a bit.
If you show your gun and he leaves and calls the police, giving them a description of your gun and yourself as well as your address and saying he mistakenly approached your home and you brandished a weapon on your front porch, you are going to be doing some explaining. You may go to court on false charges. You may loose your weapon and your right to carry. It's his word against yours, and he made the complaint. Don't expect him to be truthful or a gentleman about it.
Every situation is different, but I cannot think of a generalized scenerio where tipping your hand would be in your favor.