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.
Why in this way is the voluminous great bound sūtra in atoms’ interiors and not [unbound] for the benefit of all sentient beings?
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.
He breaks the atoms sending forth the bound sūtra for the benefit of all sentient beings. [O] Bodhisattvāḥ!
This creates the most ambiguities here:
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).