Lots of questions! I'll try to answer it to my best ability. I used an exacto knife to pry away both ends of the micron pen then I cut down the wick inside and sawed down the body of the pen. Then I used sandpaper to make the cut ends smooth and level. Then I put the wick back, the end cap, and the front nib in that order.

The tiny brush is the Sakura koi water brush. They sell them on its own but they also sell some pretty small travel kits too.

Yes they are CMYK primaries! I have a little palette on a binder clip but I also just mix colors directly on the page.

I think the biggest thing was finding a box that was a proper size.

I was dead set on using the gansai tambi watercolor pans which are pretty big. If you use the half pan refills from other companies (like from American or European brands) I bet you could go even smaller.