This all sound very good to me.
There should be a low-limit of 10-20 duress from recuperation, beyond which abilities are needed.
The issue with Will and Lore coinciding with low and high duress is that it skews the Blightmage and Faithful. I see you trying to address that, and it's where I am having trouble.
Duress reduction should be low, or max reduce to 1-2 so that gradual duress gains aren't trivialized. Also a good idea to allow players to choose weather or not to use it.
Sanity checks can be tied to Will, and perhaps some saves to avoid duress. To counter this, there should be Lore abilities which can artificially raise duress or buffer it at high amounts somehow,
Players are likely gooing to build around a "sweet spot", but allowing too much regulation goes against the principle of surviving by the skin of your teeth.Maybe each class has unique ways to self-boost duress.
Warriors can convert damage into duress, and even self harm. Maybe they enter a frenzy which boosts duress for a time, allowing them to access higher abilities, but with some drawback.
Faithful can take the duress of their allies, simultaneously relieving them and boosting their own levels.
Blightmages can craft stimulants, or absorb arcane energies from the maze.Focusing on secrets of the maze might allow access to greater magics, while draining their energy or sanity.
Mazeborn have duress gain build into their mutations, but they might also be able to metabolize reagents differently for effects.
The Haunted commune with and command spirits. They can probably drive people crazy naturally. Alternatively, use spirit points to cast beyond your normal range.
The big possibilities I see are
>self exposure to maze shit
>using duress powers against yourself
>self-harm
>taking duress from someone/where else
>Drugs. lots of drugs.
On the other hand, we could always say "fuck it" and just make players experience the progression of duress unaffected.