You made a mistake, you owned up to it. You are working hard, in marriage counseling, to fix this.

What could my partner do, to leave me, feeling beautiful, adored, etc...knowing, 1) that he has seen explicit material of other women, on-line? (I am presuming, no-one that he has ever met, or has a chance to meet?)

I would, take the time, to realize this about myself. Accept, that he's peeked at photos, and appreciate his honesty and commitment to me.