The article says nothing whatever about taxing the wealthy. It is about increased income tax rates. The measure of wealth is wealth, not income. Income tax is just a way of pretending to tax the wealthy while not actually doing so.
Yes, income tax rates. It is evidence that raising tax rates doesn't always raise tax revenues, in fact, usually the opposite. In most cases it is the wealthy who have the higher incomes.
No, that is objectively false. It depends on the marginal rate, elasticities, etc., but usually a higher tax rate will bring in more revenue. We would have to look at the full picture of tax and regulatory changes to see why revenue fell in this particular instance. There is likely another explanation. Yes, wealth and income are correlated, just as in most cases it is older people who are wealthy. That doesn't mean taxing people according to their age would constitute taxing the wealthy.
Your article in the OP is guff. There's no reference to tax analysis, only to poor secondary sources such as the Daily Telegraph. Can you refer directly to a IFS study that shows the 50p tax rate has reduced revenue? You have to be very careful as even Laffer Curve analysis (given its argued to be multi-peaked) can support tax increases
