As far as Khensu's old breastplate goes, that's up to DEFCON to make a call on that.Unless somebody really needs the cash, Avron wears a breastplate(currently +1). He would greatly benefit from the other. If we have diamond dust I'll probably go with: restoration, remove disease, and a third one unchosen(thoughts?). If no diamond dust then, locate object.
Regarding the third spell for Avron to learn ... if we can get a scroll of halt undead made by the caravan's artificiers, then I would recommend that Avron learn that since that would give us some nice battlefield control options.