| this "fish" here refers to the meat of the fish, not the whole fish, and so it should be uncountable |
|
Yes.
some isn't really unspecific about types of food. It's unspecific about the amount.
When you use "it", you mean "that
kind of food (that is,
fish)". When you use "some", you mean "a certain (indefinite)
amount of (fish)".
I don't mind having [it / fish / that kind of food] once in a while.
I don't mind having [some / some fish / a certain amount of fish] once in a while.
Note that
it is like a noun;
some is like an adjective. So, with the right grammar, you can have both:
I don't mind having [some of it / some of that kind of food / a certain amount of it / a certain amount of that kind of food] once in a while.
CJ