Build Your Own SLA/SLS

I completed the physical build and now working on the projector.

I had modified an old Dell 1410X DLP projector in order to focus near distance. Appreciate if anyone can help me with these questions

1. How much should the projected area cover the mirror hanger? Does the projected area determine the XY resolution?
2. The focus on the mirror is not fully focused, either the top or bottom part will be in focus. This is due to the angle of the mirror hanger. Is this normal?

Thanks and appreciate if anyone could help me out.

The projector shouldn't focus on the mirror. That being said, the top (closest to the vat) should be almost in focus and the bottom well out of focus. Think about focus as the lens bending light so that, no matter where on the lens the light is passing through, it will hit the same point on the focal plane (bottom of the vat). So the bottom of the mirror will have the light spread out still, but it it furthest from the vat.
The image projected on the mirror should be a trapezoid in shape with the top being almost the width of the build area. Obviously the bigger the build area, the lower the resolution. Double the width and it halves the resolution.

As you can see, I am new with this. Thank you I will give a try.