That assumes that in increase in monetary base is not matched by an increase in goods and services - you cannot just ignore that part. Also, scarcity as such has no value whatsoever.

FX rate evolution is linked to many things (and sort of a random walk anyway) - I'd say you typically need quite high inflation/rates to see devaluation in line with uncovered interest rate parity type views, short-term it could also work the other way around at times.