i've never heard of anyone santizing flavoring extract.
+1 to a little bit goes a long way
you will want to experiment though. i'd recommend taking a couple of measured samples from your carboy and adding different drop amounts, see which sample you like best. do the math and extrapolate that over the whole batch size...and to answer your probable follow up question, yes you may end up doing like 60 drops from an eye dropper into your batch..but at least you'll have a good idea of what you're going to come out with...