Both in grammar and in meaning, "to eat something" and "something to eat" are different things. They do sound very similar in English (not so in other languages), but they are not. Imagine the cases:
You want "something to eat", so you can take it as provision on a trip, or in order to give it so someone else.
You want "to eat something", because you are hungry now.
In the first case, what you primarily want is the SOMETHING, which also happens to be edible. In the second case, what you primarily want is TO EAT, so your focus is on the activity of eating, which also happens to need a something.
To be very technical, in number 2, you can pack provisions because you want to eat something (later). Consider: 'Why are you bringing fish to the cabin? You know I'm fishing.' 'Because I want to eat fish (and you rarely catch anything)'.
Most often, the English present tense is talking about the now, but not always.
But you are absolutely right that the object of 'want' is 'something' in the first case, and 'to eat' in the second case.
And thinking about it more, in 'I want to eat something', the subject of 'to eat' has to be 'I'. The sentence could be crudely expanded to 'I want me to eat something'.
Is Finnish the same as English, in that the subject of an infinitive verb is always the same subject as the main finite verb, unless another subject is somehow specified? English specifies another subject by putting an accusative noun right before the infinitive.
In contrast, 'to eat' in 'I want something to eat' can here be fairly equivalent to the passive infinitive 'to be eaten', with 'something' as the passive subject. Therefore anyone could potentially do the eventual eating, not just 'I'. The agent of 'to eat' doesn't have to be the subject of the main finite verb.
Of course, another interpretation of the English 'I want something to eat' can have an animal 'something' as the subject of an active infinitive 'to eat'. But it isn't nearly as common to intend a sentence to have that meaning. I'm not sure how that would translate into Finnish, perhaps 'Haluan, että jokin syö'?
Good point(s). "I want to eat ..." can indeed refer to a future use. But the object is still the fundamental difference between the two and therefore they are not equal as translations. And in order to understand "syödävää" in the sense of "edible / to be eaten", it is right that option 2 is marked incorrect.
PS. Your last paragraph is a nice observation, although seems to point to a use in the horror genre rather than to a nature lover. ;)