Can you let go of the expectation that child will sit at table for a proper family meal time till they are quite a bit older? If you provide them with enough food and enough choice of food so there'll be something they like (rice is rejected again? ok, well here's some cold pasta from the fridge which you know always works...) which they can choose to eat, or throw on the floor or eat later or eat off the floor (All good for the immune system) then they won't end up malnourished.
I suppose I'm suggesting RELAX!!! Trust your child, and follow their lead and life will be much easier.
You really don't have to impose an expectation of a certain kind of meal time at this point in their lives.
Remember that children have tiny stomachs compared to ours - they often prefer to eat lots of little snacks than great big official MEALS 3 times a day.
1) when you act in a manner which is apparently irrational to the child, they will push and push and push around that area trying to make sense of it. Why is throwing some things ok and some things not? Is it just when I'm in this chair? Or is it when Daddy is here? Or... It's not so much "pushing your buttons", though lots of people interpret it that way, it's a rational creature trying to make sense of arbitrary rules made by people in positions of power over them. When that's happening, it really helps to take the child's "defiance" as a clue that you are doing something they are not ready to understand, I think. (and remember they don't speak English yet. I was with the mum of a 7 month old in a cafe recently, and she solemnly and s-l-o-w-l-y and LOUDLY explained to him that if he dropped his rice cake it would have to stay on the floor because it's dirty down there and I just thought WHAAAAAT????? spread a spare muslin over the danger zone, you idiot! You might as well be speaking mandarin chinese!)
2) If your child wants to do something you are resistant to, find a safe way of giving them as much of that as they want. They are learning learning learning. Yes, you might not manage it the first time it occurs but by the second or third time, you need to find some way of making that situation happy for everyone. Child wants to walk by busy road? Fine, buy toddler reins. Child wants to throw food out of high chair? Fine. Find even cooler stuff to throw. Or cook a whole packet of tesco value pasta - they'll have a job throwing more than £1 worth on the floor and you can scoop it up and let 'em throw again, and in 2 years time, you'll look back nostalgically rather than in sadness at the textures-and-gravity-are-fascinating phase.
THere's a wonderful book by Deborah Jackson called something like "Do not disturb" (or maybe that's the subtitle) which is all about how to support your children in living and learning according to their own goals, facilitating their dance with the universe. A similar but much more dated in style old book, which might still be in libraries is Alison Stallibrass's The Self-Respecting Child.