so that's the answer that should be agreed upon and not nonsense
You're trying to mix and match too much. The answer for why shrinking saved him, in the Marvel Universe, is because "Being that small caused the force of the blast to repel him away instead of enveloping him/cooking him, and he survived the fall because he's tiny and *explanation for why tiny things survive falls/etc. here*." That's their answer. They decided the physics of the blast work that way. Trying to apply "Well, no, that wouldn't work in real life" is just met with "It's a superhero movie and they decide what the physics are." The reasoning is based on actual science, it's just obviously blown up to ridiculous comic book standards.
EDIT: The point is there is an actual basis for why shrinking saved him.
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