1) I'm not assuming anything, I asked for a source for the 200 million number and then provided other sources with lower numbers, If you have a source with different numbers, I'd love to see it.
2) "still an order of magnitude more than police/military"
Think about it for a minute. How likely is the average gun owner to answer truthfully when a stranger calls them up and asks if they own a gun? Hint: not very.
We could try using the Fermi estimation technique ("how many piano tuners are there in Chicago?").
270 million guns / claimed 80 million gun owners -> mean number of guns owned per owner is ~3.3. That seems high. Most gun owners I know own one gun. Some own two. Some own more, but I would bet money that the mean number is closer to one than it is to three.
Since we're using anecdotes - I know and go shooting with a lot of people, and I don't know a single person who only owns 1 gun, it is either 0 or 2 or more (I personally own 3).
The reason is that different guns have different uses. If someone is concerned about personal protection, they'll have a handgun. A big rifle is useful for hunting or just messing around, but the ammo might be expensive (ammo for my M1 Garand is over $1.25 per round!) so someone might have something like a .22 rifle (ammo has historically been less than 10 cents per round) that can be used inexpensively for fun. If you hunt birds a lot and/or like to shoot clay pigeons, you'll also have a shotgun.
Most gun owners live in urban areas (which makes them even less likely to answer telephone polls honestly, particularly if there are local restrictions) and don't "go shooting" or hunt.
If you hang around with woodworkers, the number of hammers owned is going to be more than one. If you're talking about random people, it's going to be much lower.
I think it is important to distinguish between urban and suburban areas, in which case suburban areas actually have the most gun owners (since they contain roughly half the population, and suburban households are more likely to own a gun than urban households) and this is where I'm drawing my personal experiences from. Due to fewer restrictions and more places to shoot, suburban areas are easier places to own one or more guns.
At any rate - 3.3 still seems reasonable to me. Although I'm not incredibly confident about it, your anecdotes and assumptions aren't enough to convince me that it is substantially higher than the actual rate.
We could try using the Fermi estimation technique ("how many piano tuners are there in Chicago?")
I have to agree with suresk people, out of all of the folks I know, the number of guns is either 0 or >1. I don't know anyone with just one gun. I suppose if you divided the number of people in a household by the number of guns you may get a number closer to 1, but that means assigning gun ownerships to babies.
2) Even using your number, it's still 80 million compared to 2 million (and not all of those two million are going to go along with it anyway).