To answer your question about Lawbreaking: Illusions break none of the Laws by default, though specific mind-manipulating ones could in theory. Glamour, however, most certainly doesn't.

Besides which, as a changling rather than a wizard, he's not bound by the laws of magic and doesn't need to worry about Lawbreaker.

I would think that guilt is just despair turned inward after you examine your own actions, but a strong case could be made to the contrary.

You might examine the Skavis faction with "Guilt = Despair" as if these Skavis were simply connoisseur's, or picky eaters so to speak. As if the various kinds of guilt, despair, and depression simply having different "flavors".

If you take that and look at a support group from the perspective of the Skavis, just imagine them like you would an all-you-can-eat buffet and things get...nasty. Especially if any of the characters are in, or have loved ones in a 12-step program of any kind.

...because, you know those programs never work right? ...but people go anyway (take the cynical view and realize the extreme would simply be a satisfying meal).

Top that off with the simple fact that people who die after meetings because of the same things they were going to meetings for (AA attendee drinks himself to death, DUA attendee ODs, etc...) would drive even more people to seek "help" with minimal prodding from the Skavis once word got around.

Kinda scary now that I think about it.

Been working out the character kinks on my Librarian Wizard (known so far as "the Archavist") in our Magical Spokane game.

Problem 1: Nothing he uses should be able to harm books unless something extremely unusual happens.
Problem 2: Even if something unusual happens and he finds himself backed up against, oh say, a bookcase (worst case scenario in his eyes) his shield, at the least, should not harm any nearby books.
Problem 3: If his defensive rote works successfully, it should damn well not put a mark on anything inside the library. Especially the books.

I found an answer to the above problems in the 2nd Edition D&D Psoioncs Handbook. I can't remember the name of the power, but there was one that created a barrier around the psion consisting of "elastic air" that contracted when a projectile attempted to pass through it. I figure his rote affects the air around him changing its properties to increase the action of friction on objects passing through it, slowing them down and eventually stopping them completely. Visually, things like shrapnel, bullets, etc will hit the shield and the impact would send circular ripples through the area of the defensive field as the kinetic energy of the projectile was bled off and dissipated (think Neo stopping bullets in the Matrix).

After the magic creating the shield dissipates, everything held in the air just falls to the ground.

Anything with its own locomotive power could just swim through the shield I guess, but anything small would have a hell of a time breathing (goddamn bugs).