Yeah, your picture is actually a bit better than what I got when projecting onto the wall (I learned very quickly that my wall is actually not very flat). I saw a huge improvement when projecting onto a screen compared to the wall. From the looks of it, your wall isn’t totally flat either, since there is some curvature in the horizonal lines. My guess is that if you deal with the curvy wall effect (causing curved lines), you won’t have much issue focusing after that. nixapatfan is right though, a slight amount of defocus at the edges relative to the center is almost inevitable, but shouldn’t be noticeable to most viewers.