1. Which is more important, presentation image quality or movie image quality?
2. You say your screen is 10' wide by 8' tall, that comes out to a 154" diagonal screen with an aspect ratio of 1.25:1 That is an odd size for your PJ which has a native AR of 4:3 (1.3333:1). Are you using a 4:3 image and just not filling the screen?
3. Are you going to roll the paint or spray it on?