IIRC (Mine is currently not handy), there is also some sort of focus related adjustment in the service mode OSD. I would think the focus pot on the flyback would have more effect. Did you say you turned the focus pot on the flyback, and it had NO effect, or were you just not able to make it "good" using that method?
There is also a moire adjustment in the OSD. This purturbs the picture some in order to reduce the appearance of moire patterns, but can cause things to look blurry to some (for others it just looks really jumpy). Perhaps those got set wrong?
Like QRZ said, this could also be a convergence issue given your description. This looks different, but may appear to some as blurriness. A pic would be most useful. Try to grab it with both a known good test pattern such as a grid as well as the OSD up.