As far as I know, money only gets devalued when more is added in circulation, not when more is paid out to workers.
Not necessarily.
The idea that there was a concrete link between the money supply and inflation was essentially unhinged in the 90s, which led Milton Friedman to renege on monetarism.
I think it has something to do with the demand for money.
Also, a rise in minimum wage would probably result in an increase in the monetary base, thus causing inflation, or result in slower labour growth, thus causing unemployment.