Haven't had a closer look at the schems, but picked up one question in them: Yes you can have encoders and buttons on the same DIN module. As you correctly noticed, encoders need 2 pins, buttons need 1 (hence 14 + 9 * 2 = 32). Encoders HAVE to start on an even pin (if you count from zero) ie, 0, 2, 4, 6, ...
Bankstick: Unless you want to store some kind of patches, you don't need one. Since a bankstick doesn't require anything but the IC itself, it's easy to add later on if you feel like it.