We've got duplicates of many toys because they are into the same thing and it caused lots of headaches for me when they would fight over the one Thomas. But then they would fight over the one that didn't have chipped paint
I think it's normal for them to be possessive of their toys or favourite things. Is he like it with his room too?

I don't offer a second "meal". If they refuse their dinner then maybe a salada or piece of bread. Does he eat much during the day? C eats a big breakfast and lunch with grazing all morning so I'm happy enough that if he goes to bed without eating much dinner, he's really filled up enough during the day.