Great game! cant wait to run it!
Id like to say, i think it is not an improvement to remove "mad". for one thing, "drained" is a much weaker term, and it is not at all clear how it differs from exhausted, except that it involves will rather than strength. it is stated to be a "serious" condition, which exhausted is not, though if they are degrees of the same thing, exhausted sounds stronger. it doesnt give a clear idea how "drained" is to be roleplayed, while "mad" evokes strong roleplay ideas in most people.
keeping "mad" emphasizes the idea that just about everything in this world is more powerful than a mouse, which seems to be a strong theme of the game. (i suppose others may differ). "drained" doesnt at all evoke this; it seems to evoke the idea that magic is a thing not terribly taxing to the mental tolerance of a mouse.
the connection should be maintained between the "attribute score loss" section and the "magic" section. where before they said respectively "reduced to madness" and "mad condition", now they say "reduced to insensibility" and "drained condition"; there is no longer a clear mechanical or thematic connection between the two. it would sound pretty weak if it said "if WIL is reduced to zero, they become drained".
I like the cthulian vibes of having madness as an explicit possiblity, but if you are intent on excluding it, i suggest replacing the "drained" condition with the "insensate" condition (or some synonym). It maintains the clear connection to "reduced to insensibility", and is much more obviously a mental condition, a failure of will. "insensate" would mean the mouse is confused, not fully sensible, has lost critical thinking, isnt acting rationally.
alternate terms could be: senseless, insensible, witless, irrational, stupefied, panicked, stricken, spooked, shell-shocked, harrowed, perturbed, scared shitless, hysterical, stunned, timorous, frantic
These suggestions are given with the greatest respect for your work on this excellent rpg.