Learn French: Elle a dévoré le document au point qu'elle n'a rien entendu. - She devoured the document to the point that she heard nothing.

Au point que (to the point that) introduces a consequence that is a definite, realized fact—she genuinely didn't hear anything. Because it describes an actual result rather than a goal, doubt, or emotion, it requires the indicative mood.

Could we use à tel point que in this sentence instead?

Absolutely. À tel point que means the same thing and also takes the indicative mood. You could say ...à tel point qu'elle n'a rien entendu, which adds just a slight bit more emphasis on the intensity (to such a point that).

Why is rien sandwiched between the two parts of the past tense (n'a rien entendu) instead of at the end?

In compound tenses like the passé composé, short, common negative words like rien (nothing), jamais (never), and plus (anymore) are placed directly after the auxiliary verb (a) and before the past participle (entendu). It is a helpful rule to review because English speakers often want to put them at the end of the sentence.

Is dévorer a common metaphor for reading in French, or is this an unusual phrase?

Just like in English, dévorer (to devour) is a very common and natural metaphor in French for reading something eagerly and quickly. You will frequently hear people say they devoured a book (dévorer un livre).