As a native I dont make any difference in pronouncing the F or V. Perhaps a logopedist would know the difference, but I think it doesnt matter for learning the language. Btw. you probably meant verdrietig (sad), instead of verdertig (no meaning)

I pronounce all the words you mention with 'v'. I never even noticed that the Dutch do it differently.

It mainly depends on what part of the Netherlands you come from. In some parts it is pronounced as a ''F'' indeed, while ABN (Standard Dutch) dictates it as a V, if I'm not mistaking. Anyway, I pronounce it as a V.