That's a tough one. Proteins are a much more useful source of energy and nutrients here. There are limits though and then it doesn't really matter how you get your calories.
So obviously carbs are cheap food and pack a lot of calories which might be beneficial in this scenario.
You are right. I can't argue with that, but I would be careful with this as general advice.
It depends on the meaning of amount. By volume no, you can continue to eat like always if you adjust the food itself.
Technically yes, it is a food restriction, but in the end it is especially a calorie restriction which is the important part.
You are absolutely correct though.