3. Yeah, those comments did a lot of re-defining of terms, and in some cases, dismissing data.
The guy asking the question uses "national income" in the question then defines that as GDP in his answers. A commenter rejects GDP as the definition of national income and provides his own definition of it. I think the guy who asked the question gets to decide what he meant by national income. But if he reworded the question to say GDP rather than "national income" he could avoid this argument.
In objecting to the Social Security question, one commenter just summarily dismissed income from interest on the SS trust fund. This has become a limited right wing talking point, to say that the trust fund doesn't really exist because it's in the form of government bonds--money the government owes to the government. You don't hear this much because it implies government bonds are rubbish, when most investors consider them the safest investments available, and it implies the right wingers want at some point to "disappear" the Social Security trust fund.
I think the writer overstepped on the health care question. He attributes the change, in 2009, from increases in health care spending no longer exceeding increases in income to the effects of the Affordable Care Act (Obamacare). But that didn't go into effect in 2009. The law didn't pass until 2010, and many provisions have yet to go into effect.