Why does investment income reported on a 1099-MISC result in $80 more tax due than if it was reported on a 1099-INT or 1099-DIV?

Qualified dividends and most investment sale income is taxed at capital gain tax rates, that may be less than your ordinary tax rates that would apply to income reported on a form 1099-MISC. 

Yes, but how do I correct this situation: Apparently my broker loaned out some of my stock to a short seller.  I received payment of a dividend paid while on loan as a substitute payment reported in box 8 of a 1099-misc.  How do I get this payment changed from ordinary income to qualified dividend?

You can ask the brokerage to send a corrected 1099-DIV.