Hi Michael, that is a decent match and is a good entry to tech bindings (not least because of the ease of said entry). The 100mm is the right brake size and the precut skins work great!
Hi Sam, looks like you found them. They are listed as Radical Crampon Receptors.
Hi Chris, it's in the same ballpark out of the box, but Atomic used "magic-shell" so it can mold around your foot.
Hi Jeff, SCARPA uses similar lengths across their line of boots, but the widths can vary. The Alien is noticeably narrower than the Maestrale in the same size, but about the same length.
Hi Jason, the small should do just fine for you.