Yes, there's a movable divider on all the center seat pairs. No worries there.
I would definitely take the hotel if I were you. 9 hours is way too long in the lounge. I decided I didn't feel like dealing with immigration, etc. a few weeks ago on a 6hr40 connection and was really wishing I'd chosen differently a few hours in. There's very little to do in the DXB F lounges. Also, there are no private slumber rooms in the lounge, and the communal "quiet rooms" for resting are woefully inadequate and far too public, IMHO.