TAC is largely AdSense partner payouts - and likely things like Chrome distribution deals and Android partner agreements now. Saying "net income grew almost as much as TAC" is basically saying "Google's AdSense, Chrome, and Android businesses are a healthy and growing segment of its total revenues."
Note that you can spin this to look bad for Google either way. If TAC was low, it'd be "Google gyps their AdSense partners, and soon there'll be a publisher revolt", something I've occasionally seen complained about on HN. If TAC is high, it's "Google's numbers don't look good; clearly their business is in trouble." The numbers are what they are; if you want a useful picture of whether to invest, you need to understand the business better than that.
No; $1 returned $1.2, which is better than any bank at the moment; and these are marginal numbers which understate the underlying profitability (i.e. they are like the derivative of the costs and profits).
Note that you can spin this to look bad for Google either way. If TAC was low, it'd be "Google gyps their AdSense partners, and soon there'll be a publisher revolt", something I've occasionally seen complained about on HN. If TAC is high, it's "Google's numbers don't look good; clearly their business is in trouble." The numbers are what they are; if you want a useful picture of whether to invest, you need to understand the business better than that.