what's the difference between the stats/character aspects fetish, sluttiness & lust?
Lust is meant to reflect the Sorceress current, immediate sexual desire, while sluttiness refers to her openness to lewd situations as a whole.
In practical terms, with high lust, the Sorceress may be locked out from choosing the low lust option during a decision. It's easier to raise and lower this stat as a result.
Sluttiness informs her attitude as a whole, so then the stat is higher, she may have more/different commentary during scenes, and some scenes will require a higher slut state to unlock at all. While it is initially easy to raise her sluttiness, there will be few opportunities to lower it as the game goes on, and how high it is will have an effect on the games ending.
That's the idea at least, the system is currently under developed and I'm working on improving it