I do not believe that there is a maximum amount of vitamin K that a person on warfarin can consume.  There are many vegetarians and vegans that consume huge amounts of vitamin K while taking warfarin.  In my eight years of managing warfarin, I have found that if someone is given a strict diet, they will stay on it for a week or two and then drift back to what they like to eat.  So my idea is that you should adjust the warfarin dose to account for the vitamin K in the diet, not the other way around.