This was maybe a foolish literalism. I cannot edit the post anymore though, alas.
In the above, "the sūtra bound" is 經卷, lit. "sūtra coil/roll/coiled/rolled", referring to a large wrapped sūtra. Placing the adjective after the noun creates confusion in the passage, it might be a Gallicism of my part perhaps mixing with a want to stick to the Chinese ordering somewhat naïvely perhaps.
Read it instead as "the bound sūtra" in the sense of a huge "wrapped up/rolled up" sūtra.
云何如此廣大經卷在微塵內而不饒益諸眾生耶。
Why in this way is the voluminous great bound sūtra in atoms’ interiors and not [unbound] for the benefit of all sentient beings?
我今應當勤作方便破彼微塵出此經卷饒益 眾生。作是念已。爾時彼人即作方便。
I presently shall muster great perseverance and power to break these atoms and send forth the bound sūtra for the benefit of all sentient beings. Then that man promptly musters power.
破壞微塵出此經卷饒益眾生。佛子。如來智慧。無相智慧。無閡智慧。具足在於眾生身中。
He breaks the atoms sending forth the bound sūtra for the benefit of all sentient beings. [O] Bodhisattvāḥ!
This creates the most ambiguities here:
見此經卷在微塵內。作如是念。云何如此廣大經卷在微塵內而不饒益諸眾生耶。
H[e] regards this sūtra bound in atoms’ interiors. He speaks aloud like this: Why in this way is the voluminous great sūtra bound in atoms’ interiors and not [unbound] for the benefit of all sentient beings?
When there are two different meanings of "bound" employed, one in [square brackets] all the worse. "Bound" in the sense of the sūtra "bound" in the atom's interiors and "bound" in the sense of the sūtra "bound" (meaning "wrapped (up)" here, 經卷 from above, he breaks the atoms sending forth the great-wrapped-sūtra for the benefit of all sentient beings).
My apologies.