Also, is it true, as claimed in the article, that WW2 got the US out of the Great Depression? This has never seemed plausible to me (get richer by doing a huge amount of non-productive work?), and wars don't usually seem to be great for the economy.

It's sort-of plausible, because the GD was due to a severe shortfall in overall nominal expenditure wrt. the prevailing level of prices and wages. The original cause of this shortfall was a series of mistakes in monetary policy; however, increased deficit spending in WW2 could have made up for it.