The first cut is indeed the deepest, about bone deep. Then you have to spend loads of time in hospital and undergo exploratory operation to check for damage (none so phew). Will post photos as soon as the bandaging will allow.

Leatherman blade into the fleshy bit of the thumb, apparently the whole opposable thumb thing is important.

Get physio on it.

Pfft. Try having someone attempt to bite your finger off, involving degloving (look it up if you dare). Sharp blade, clean cut? You lucky, lucky…