Baldur's Gate : The Sword Coast Chronicles : NWN2 Persistent World

So, the level 1 arcane spell "Disguise" says the following.

"You magically alter your appearance. The caster decides what to disguise and may at any time remove the disguise. Unlike regular disguises the Disguise Other spell creates an illusion which can be detected and dispelled. The detection DC for the disguise is the spell's save DC - 10, raised up to your total DC depending on the targets disguise skill."

I need some help understanding this description... first of.

"The caster decides what to disguise" = I want to alter the appearance of my palemaster arm... is THAT allowed? a section of yourself, or do I disguise myself as how I would look without a necrotic limb attached...?

Second.. the "Unlike regular disguises the Disguise Other spell" = Are we still talking about disguise or some other spell called Disguise Other? ...

Third... "The detection DC for the disguise is the spell's save DC - 10, raised to your total DC depending on the target disguise skill" = So... if I had dc 30, that would make it Disguise spells dc 20 (30 - 10), then I'd need to also have 30 in the disguise skill, to get the spells dc back to 30? - Also what if I had 40 in disguise? could the spells DC go beyond my own total DC?

The whole disguise system, including the spells are still in the works. Dont read in too much in the current description

Not sure about the rest of it, but as to your first question...

There is no real reason you couldn't disguise yourself as "yourself before you were a palemaster."

Of course, you could also just wear long sleeves and some gloves...and a LOT of perfume. It's like wearing a mask; disguise skill or not, if they can't see your face they can't see your face. Even a spot modifier of 1,000 doesn't grant x-ray vision.