When I run into any feeding questions, I go and review Ellyn Satter's advice. I have her book Child of Mine, but a brief outline of her work is available on her website:
When we are emotionally invested in how much our kids eat (and who isn't, to some degree) it's all to easy to create pressure that kids automatically resist. This can lead to "you can't make me eat" tactics that result in waste.
Even being too flexible can backfire. Positive pressure is when we invest too much into making eating pleasant (i.e. menu planning centered on their likes/dislikes, rewards, cute food, encouraging bites) Kids can sense the pressure to eat, even when we ourselves didn't realize it was there.
A few concrete suggestions, get rid of grazing and try limiting his choices to selection at the dinner table, not at the store or in the kitchen. Provide a few options at the table and let the family serve themselves from serving bowls/platters. Make sure it's food you're willing to eat also, not just "kid food," sit down and eat with the kids, even for snack if you can. Eat without comment, talk about other things. If they make a fuss, just say they don't have to eat it, but it stays on their plate after they choose it. Give them the chance to help put away leftovers, it's a wordless way to get them thinking about where that food goes.
It is painful to throw anything away when you would much rather not waste a bite, but working on their food acceptance is the road to reducing waste. You can guess how much the family will eat without worrying too much about what individuals eat if you refuse to do "custom orders."
I hope you find some of the above useful, Ellyn Satter's book has been a wonderful resource for our family ;-)