If you are going to make the decision to use deadly force on a person, do not worry about how far the bullet will travel and if it breaks up before it goes into your neighbor's house. Once you pick up your weapon only 2 things should enter your head. 1. Is the person in my sights, if not do not pull the trigger. 2. The person is in my sights, pull the trigger. Everything else is moot. So get the most reliable, most easily worked on weapon you can find with enough stopping power to drop a tweeked up maniac. Uncle had it, the 1911 45 ACP. Get 2 magazines and Trijicon night sights. You can customize one to fit your needs easily. Ammo is available everywhere and is cheap, Dirt Cheap as someone has pointed out. Get 185 GR Silvertips for the first 4 shots and 230 GR FMJ for the rest. You can figure out what to do with the FMJ.
I have had no problem with the two questions, so the 1911 is it.
The only advice I can give you is practice, practice, practice and when you are done, practice some more. Because when it happens, you will need to rely on memory, not about what you are thinking about in your head, which will not be what you think you will be thinking. You will not remember what you were thinking.
Only my 2P.