How do we reconcile God’s sole knowledge of the unseen with "God's wonder at the Companion's action with his guest when he mimicked eating but did not eat," given that God knew this beforehand?

The attribute of "Al-Ajab" (wonder/admiration) ascribed to Allah Almighty signifies "wonder of approbation" (عجب استحسان), not a wonder of astonishment or ignorance. This attribute is affirmed in the Quran and Sunnah (definition). Therefore, it is impermissible to interpret it as ignorance or astonishment. Rather, it denotes glorification and approbation of an action, coupled with Allah’s pre-existing knowledge. To address obsessive doubts (waswasah), one is advised to seek religious knowledge, seek refuge in Allah, and desist from indulging in such thoughts.