Also, the “m” in “thumos” is not part of the root, it comes from the suffix that is used for this particular (Greek) noun-form: PIE *dhu-mos. So it shouldn’t exist in the English, which doesn’t adopt the form with the *mos suffix. Note that Greek forms from the same root which do not use this suffix don’t have a medial nasal: e.g., the verb thew (“to run”). Same with, e.g., English “dew.”

OED traces “dust” back to OE dust < earlier *dunst, as you note. Wiktionary goes back from there to Proto-Germanic *dunstiz, from the e-grade PIE root *dheu-. Is the "nstiz" some sort of (Germanic) suffix? I'm unfamiliar with it.

By the way, I've been greatly enjoying the philology posts.

Dentes = teeth