I think that if you've both sat down and agreed to a divorce, then the being married and in the same house rule you agreed (probably at the very beginning of your relationship) may not apply. Circumstances change and whilst you shouldn't have invade his privacy because it's his own space etc, it's also not necessarily your business because you've agreed to a divorce. It's not on paper obviously but if you've agreed it between yourselves, you maybe need to discuss your married/same house-seeing other people rule again.

Sorry if it sounded blunt/harsh. Didn't mean to sound mean, just saying it how I see it.

Hope things work out for you as best they can.