Look at your baby. Does he have a good colour? Is he happy and alert? Is he as heavy as he was a month ago (ie not losing weight?) Then he's probably fine.
Babies and toddlers know very well how much they want to eat and, I think, what they need too. If they are offered healthy choices, they may have favourites for a while but will often vary their own diet. People who draw up weight charts should be offering guidelines, but if your baby is healthy and happy and eating something, they should not be taken too seriously.
My dss were fed on demand for 2 years and never ate more than 2 meals a day, as toddlers. It's only once they were weaned and then started school that I have found they need a third meal. 3 meals a day is an odd habit for developed Western cultures. It's not essential. You could cut out or delay the morning feed and have breakfast instead, or you can just let him have a lighter breakfast. Either should be fine.
Do relax and go back to enjoying your baby. Don't let anyone frighten you into being like this. They have obviously tapped into something powerful in you. (Personally, I hate throwing away food I've prepared and yes, I've occasionally lost it like you, when an apparently hungry child turned their nose up at a meal they would have loved yesterday. Next day it would be banana sandwiches for lunch and everyone happy.) See if you can deal with whatever is making you feel guilty. You are obviously a caring and loving mum. You have not failed if your child is not eating like a horse. They can survive on small amounts of healthy food and lots of love.
Best of luck in getting back to having fun together.