I think that, in general, food contains less salt anyway and that's what you need to worry about. They were probably treating the baby anyway because they were out and about, convenience and all that jazz. You could always go armed with bags of fruit when you visit but you may not be as favourited as the nan who brings the lovely, lovely milky ways. A 1 year old should be eating around 1000 calories a day, depending on how active it is.
Home schooled??? I agree with sqad, what about the social side. I hated PE but it provides you with team building skills. You learn a lot of people skills at school. You just don't learn about life knocking about at home. I'd worry my parents/tutor weren't teaching me properly, a variety of teachers ensures you're punctuating to the best of your ability.