In your home invasion scenario the bad guy was dressed like one might expect and had an obvious weapon (confirmation). What about a better dressed bad guy with a concealed weapon? Would this cause you to go to your pre-positioned gun? Probably not.
This is an argument for carrying inside the home. If the person at the door is a stranger, one could take the precaution of gripping, but not drawing one's gun. One foot could be placed about 6 inches from the door in a position to block it from fully opening. That way, an attempt to knock the door fully open would be thwarted, and the defender could quickly draw his weapon. On the other hand, if the visitor was peaceful, he would never know that the homeowner was armed or cautious.
I like your series. Makes one think, which is the point after all. Where can one go to learn the bare hand skills demonstrated?
TH
Virginia