that all sounds exhausting, is it really that important that your dc eat what you want them to?
It probably sounds a lot worst than it is in real life, I have 4 kids (2 who are young teens) and we don't have a fight per meal! It's actually quite peaceful! There are phases when things don't work as smoothly, but they eat at home at least once a day + breakfast, I am not having a daily fight.
Bus yes, it is very important. They only have to try a little bit of everything. They have never been told to finish a plate. I am not having a child who looks down at food, saying "I don't like it" when he hasn't even tried. I am not having a child who doesn't eat vegetables either.
What's the alternative? A child who will only accept to eat biscuit and chocolate?
Following the birthday cake incident, the "I don't like it I am not eating that" have been replaced by "no thank you" . 
It wasn't random, we had to put off with horrible behaviour for a couple of weeks, and I did warn very nicely I wasn't putting up with it any longer. I don't threaten my kids, I give them a warning. They wouldn't know I mean it if i hadn't follow through a couple of times in their life, it's usually more than enough.