If my understanding is correct, Catamite allows you access to the Slutty Checks and such or fail them without failing them against your will if you have enough PUR/DIG. There's also some endings that require low PUR/DIG
Purity can't be raised, it's lost each time you suck a cock or get fucked. Facials do not lower Purity. Dignity is gained by defeating enemies by health to 0 instead of dominating or satisfying.
