@amoobaa gosh that sounds tough. Big hugs to you.
Not eating all the food on your plate doesn’t necessarily mean food waste - we plate up the main bit, say cottage pie, with what I feel is an appropriate sized portion. Then the accompanying veg everyone helps themselves to the amount they can eat. If they then need more of anything they can help themselves. But I only have control over my own body - I know how hungry I am. I certainly would never presume to know how much my OH or my child will eat!
Sadly, I know a little girl who has to eat everything on her plate before she can have pudding and she’s now on a diet at 9. And I also know an 11 year old whose mum controls what and how much she eats so that when she gets the opportunity to eat away from her mum, she binges. Not healthy.