According to Wittgenstein, the role of philosophy is to clarify meaning until statements are either scientifically tractable, or meaningless (i.e. pseudo questions).
The "disputable sphere of natural science" coincide with meaningful questions.
Wittgenstein was not really concerned by the demarcation between science and pseudo-science, but this verificationist principle was adapted by Popper into a falsificationist principle for that purpose (although Popper did not think that non-scientific statements are meaningless).
This is clearly a demarcation between science and metaphysics, and a rejection of metaphysics as meaningless.
Entity realism is a realism, and realism is a metaphysical position. Entity realism is thus metaphysics and meaningless, by verificationist standards.
I don't think the tractatus is so concerned about dogmatism or foundationalism.
You can be dogmatic about verifiable statements you do not wish to verify, and in any case it seems that verificationism requires some sort of foundationalism (empiric verification as a foundation of knowledge).
The main focus of the tractatus is not on knowledge, but on meaning and truth.
Wittgenstein would probably reject the question of knowledge as untractable: you cannot question the possibility of knowledge, because you cannot possibly "see" your own relation to the world, it is just given.