well from my own experience with my 6500ub, I think you should be fine, I used to use a 135 inch 1.78(16x9) screen with mine and only put it at dynamic during the daytime, or used living room on those dark movies that needed a bit more punch, my pj is rated at 1600 lumens as well, so I don't think there would be any difference. The farther back the pj is from the screen, the dimmer it becomes and thus can give you slightly better blacks, just like the auto iris dims to give better blacks. I never noticed a difference myself when increasing the picture size on black level, so maybe you won't either. I really love blacks as well and will sometimes turn the brightness down a hair with certain movies to increase the black level, which essentially creates a picture with some crushed blacks, but for me its a good tradeoff at times. You could certainly try this to get more black if your not happy with it. You can also adjust the dynamic mode a bit to cut down the green color which is there purposely to cut through ambient light. I believe the living room mode is more blue to cut through yellow light from light bulbs in living rooms. Calibrating them a bit will result in a better picture, but less lumens. Honestly I think most people prefer the punch of the brightness over correctly calibrated anyway, so if its not perfect in color, very few people will complain, especially since there is not another projector in the room playing at the same time to compare pictures to.
I think you will be very happy with the 2.35 screen, to me they feel more like a movie theater, and if you mask the top and bottom to hide the overspill, it will really look great.
Forgot to mention, my setup was in a living room with lots of windows and all white walls, so if you have a dark room and light control, you will be even better off