Yo homie! congrats on completing the dreaded 250 box challenge. I'm here to provide some of my critique and I hope it helps. I also just recently finished the darn thing so you and I are getting off the same stop.

Firstly, your lines have greatly improved. It went from very wobbly to pretty good over the course of the challenge. Although there is a little bit of wobble in your later boxes, I trust that you will get out of this through experience and more line making as you go through this course.

Secondly, your inner corner game in your later boxes is absolutely on point, at least looking at it with my eyes. Of course, its not all perfect. There is some "off-ness" with a few boxes. A good way to work on this, from my experience, is to use the outer lines (the non-xray lines) as a sort of guide in making the inner lines. If this works for you then it well improve your inner points. Aside from that, good Job!

Next up is that your convergence with your boxes have greatly improved as well. The earlier boxes, especially the ones marked in red, had almost no convergence and basically spread out like a peacock's tail. This is rarely present in your later boxes. I will say that the extension lines are a bit too parallel imo, if you add a bit more convergence it will look better.

Lastly, the boxes overall show very little variety imo, some pages look like they are the same box but angled in different ways, but this can easily be fixed if you keep it in mind.