You can make the screen any size you want, just stick to a ratio that makes sense or you will either have the image spilling out on one direction or have white space you aren't projecting on. 16:9 if you want to just stick to what the projector displays, scope 2.35:1 (or 2.4:1, close to the same thing) if you want to either use a lens or use zoom to show movies without letterbox bars. If you are going with scope and zooming, it is best to use a projector with power lens zoom and shift memory, or you will be manually changing it back and forth for different media.
I had the Sony HW40ES in my last theater and I loved it. It was super quiet in low lamp mode, which was very important on a short ceiling. The projector sat only a few feet above my head when sitting, so having a projector that is only ~22db is really nice. The 45 is even nicer, but I am pretty sure that like the 40, it doesn't have any power zoom or shift, so not well suited for scope screens. I skipped the Epson because of the fan noise, but you can get lens memory in the same price range as the Sony, so it is really a matter of what direction you go on the screen.
Two rows is going to be tight in that room, especially with an AT screen wall. I would do what you can to avoid placing your front row at the midpoint of the room. You are going to have room modes at 11', and probably some issues half way between the speakers and the back wall as well, so placing the front row ears at 10' could be pretty ugly. I would personally go for around 13-14' back from the front wall, and as suggested, go with non-reclining back row seating. I don't like the elevated second row seats from seatcraft and palliser, your feet can't touch the ground when sitting in them.
It is good to have space between the walls and the seats, but for 2 rows in that room, you will probably have the back row nearly pinned to the wall. As recommended, skip atmos and go with surrounds placed high on the walls angled down toward the listeners. Your width is good for a row of 4, but pinned to the back wall you will have rear surrounds blasting back row listeners if you place them at ear level. If you do rear speakers high up, do the side surrounds high up too.
Finally, while I can't disagree on doing an AT wall for speakers placed at ear level in the front, I ran a center under a 120" screen in a room with 7' ceilings and it worked just fine. I never noticed dialogue sounding too low on the screen. Just my opinion though.