It’s really best for your dog to eat at certain times rather than graze. In the wild, canines eat once a day, at the most, and ideally their stomachs should empty completely before eating again (also, after leaving food out for 30 minutes, bacteria start to grow rapidly!). Grazing can have a negative impact on their health for several reasons, but I’m not gonna drone on about all that.
Anyway, I can’t blame him for digging in his heels after you restricted his access to food, even to the point of not eating to voice his displeasure. Having it available at all times is of course very nice and convenient. But I think you can pull this off if you go slowly. If his food is available to him 24 hours a day right now, cut it down to twelve hours to start with. Pick your “goal” meal times, and leave the food down for three to four hours around that time. For example, if you plan to feed him lunch at noon, leave the food out from 11am to 2pm or so, however it fits your schedule best. Do the same for breakfast and dinner. This will get him used to going without food at certain times of the day, while still allowing him to graze for a good amount of time. I would do this for the first week, then cut it down to 2 hours per meal for the second week, one hour the third, the fourth week 30 minutes. Then you should be pretty much set.
Hopefully this will avoid a doggie tantrum. They are very good at making you feel guilty, but don’t let him pout his way to success!
Good luck!