Impressive work. I don't know much about the C64, but I thought I read somewhere that the graphics engine was not able to support the 160x168 16-color screen that AGI needed. Looks like these guys figured it out though.
The title bar in most SQ1 screen shots look like they show the score as "8 of 282". But I think the C64 glyph for zero just looks like an 8. Checking the KQ1 screenshot, which I know has a max score of 158, you can see the glyphs for zero and 8 are very similar, but the zero glyph is slightly different.
Is that how the C64 always shows the zero? That seems like a terrible design choice for font.