Corrupted Arts & Spells

A few quick mechanical questions on Corrupted Arts & Spells (from RoP:I).
In theory, someone could cast a Corrupted spell, with both a Corrupted Technique and a Corrupted Form.

Do the +3/-3 modifiers (from the spell, and from both Arts) stack into a big +9/-9 modifier?

If the total modifier is sufficient to reverse the outcome of the casting (changing success into failure or viceversa), do both the Arts and the mastery each gain or lose 5xp?

If the answer to both questions is yes (that's how I tend to read the rules) would the answer to the last question change if a single +/-3 modifier were sufficient to reverse the result of the casting (so that you could argue that the spell corruption, or the Technique corruption, or the Form corruption, but not all three, were responsible for the reversal)?

Last but not least, I don't think I understand how to classify actions as "selfless", "selfish" or "neutral". It sounds a bit like trying to classify objects as "blue" "non-blue" and "neutral". What's "neutral"? The best I could come up so far is this.
A selfless action would only be undertaken by a "generous" character, being detrimental to the character albeit beneficial to others. E.g. selling an item for less than its value to an old needy widow.
A selfish action would never be undertaken by a "generous" character, being beneficial to the character but "unfairly" detrimental to others. It would probably be undertaken by someone less scrupolous. E.g. selling an item for more than its value to an old widow who's lost her wits.
A neutral action would be undertaken both by "generous" and "non-generous" characters, being beneficial to the character, but not detrimental (and perhaps even beneficial) to others. E.g. selling an item for a fair price to a customer who can afford it.