America has more guns in fewer hands than ever before

[jimmy the one]

16. much larger increase in 'non gun-owners'

statistical: Population of US
1980 - 226.5M ..... 2012 - 311.7M >>>> Note: 2015 est 316M
Nominal owners of guns
1980 - 65.7M (226.5M * 29%) 2013 - 68.6M (311.7M * 22%)

That would be more guns in slightly more (not fewer) hands. Right?

Yes, with those numbers, better said 'at parity' with little change; I think pew is closer with near 25% actually, since a lot of teenagers younger than 18 can own rifles & consider themselves gun owners.
But realize this as well; using your stats, the number of people NOT owning guns has also gone up:

1980 No gun peoples: 160.8 Million peeps (226.5 x 0.71 = 160.8)
2012 No gun peoples: 243.1 million peeps 311.7 x 0.78 = 243)

So the number of americans who do not own guns in America today has increased by 83 million people since 1980 while the population increased by ~85 million, while the number of gun owners during same time period increased only 3 to 10 million, remaining near parity.
The trend is away from gun ownership, accd'g to pew & gss stats.
Indeed, almost the entire increase in population since 1980, can be statistically said to consist of 'non gun owners'. Accd'g to pew & gss; Yow.