I can't believe nobody asked for my input yet.
I am, after all, Tony Stark.
I'll address a couple of points I skimmed, and see what you guys can throw at the revisions and see if they hold up.
First - 1/4" steel plate behind the drywall around and under doors/windows. Unobtrusive, and adds thermal mass, so might not be a bad idea anyway. (addresses "house worth living in" being bulletproof)
Second - I'm sure an ingenious soul could rig this up, as I'm about to try once I have some debt paid down - for moltov cocktails and the like, a metal roof would itself be rather impervious, but the fuel would tend to run down into the gutters, and set the wood substructure on fire. I have all the parts in a bucket to put a roof sprayer system together, that's actually intended to lower my cooling requirements in the summer - it'll run off my rain barrels. (yes i've thought of fuel cycling through the system... it's got a bottom pickup on the last barrel in series) This would tend to drive the fuel down the roof and into the gutters, assuming you could trigger it at will - which I'll be able to do. From there, a CO2 bottle commonly used for portable "air" nailers (or a couple of them) could easily be rigged to blow gas through a small diameter pipe, perforated every couple of inches, glued to the upper inside edge of the gutter - this would keep the holes free of leaf gunk, and would flood the gutter with carbon dioxide. I'd have the end of the tube directed down the downspout, so as to flood the downspout and first barrel with CO2 as well. You'd need an appropriate pressure regulator as well, but this should certainly extinguish a single cocktail thrown on a metal roof, especially if your fascia is clad in metal, and the gutters are mounted high on the fascia. The flood of water would also cool the metal, keeping the wood beneath it from charring and catching fire.
Third - A similar arrangement to above, but an additional pipe can be mounted through the side wall of the downspouts, routed up into the gutter and down a ways, and a chemical foam fire extinguisher could easily be stuffed into the end of the pipe and triggered, filling the gutters with the foam.
The only situation I don't see being handled is a cocktail onto a deck/porch or one thrown high against a wall, involving the soffit below the gutters. This would likely require its own dedicated sprayers, since the soffit vents provide direct access to attic spaces and roof joists/trusses.
Fourth - keep 'em away from the house to begin with. I like the living fence concept, but nothing says you love 'em like automated point-defense turrets firing even something as non-lethal as paintballs. Those air/CO2 powered devices can launch hundreds of rounds per minute, and there are even kits online for building your own automated, motion-sensing, target-tracking mounts. A hail of anything coming at me is going to give me pause, and if it hurts and goes splat, obscuring my vision and impeding my motion, I'm at a serious disadvantage. If you throw in some frozen balls, or it's cold enough out, then you're hurling .50 caliber solid chunks of pain instead of colorful pigment.
Just some thoughts. The last one is a little out there, but should be particularly useful against unauthorized vehicles, since if they can't see out, they can't maneuver.