Yours is indeed an interesting story. The world is far from a safe place anywhere.
I went to the NRA link to see how they got the 1.5m figure. I would not regard NRA as conducting any unbiased research. It seems to me that their survey techniques would lead to an inflated figure. But for the moment, let's cast this 1.5 m figure as valid. For sure, it is a big number.
1.5m divided by 330m Americans gives a 0.45% chance of an American needing a firearm to defend themselves in any given year. Methinks that to have a long life, there are other lifestyle facets that will give a higher return, like eating well and driving within speed limits.
Having firearms in a house is not always a guarantee that any defence will be a successful defence. The firearm has to be appropriate and available. Pistols would be better than AR15s in this regard. And then there is a training. Being able to use a firearm effectively requires a constant update on skills AND protocols for dealing with the dangers one expects to face. And finally, there are dangerous situations where even good training and appropriate firearms cannot foresee. I would wager that, these days, many burglars carry their pistols in their line of work because they expect to defend themselves against an irate homeowner with a gun.
And, of course, having a firearm in the house increases the chance of an accidental shooting. Is this chance greater or lower than the 0.45% of the NRA? Even if lower, accidental shootings will deflate some of the true effectiveness.
-----------
Now don't get me wrong here. I'm not trying to take anyone's guns away. If they want a firearm to stop a home burglary or a little worse, they should be allowed to do so.
I would even call myself a freeloader in that firearm enthusiasts are putting some fear into the criminal world not to mess with average people--because one never knows which houses have guns and people who know how to use them. I get the benefit of that.
All I would request is that firearm users get the proper credentials and background checks for having that firearm in their house. Dave Tomlinson's "user license" seems to be the best solution I have encountered.