In addition to higher tier customers, whoring is actually
supposed to be worse than jobs in the early chapters and overtake it later on. Goldo even had some graphs for that during early 0.2, which are now sadly lost with the old forum (or maybe he still has them tucked away somewhere?). Chris12/Ch12 also had some analysis of the same kind (and that's lost now as well), but I think it was based on either
very early 0.2 or even 0.15b.
One way to squeeze more performance out of your whores is to use either group sex or double service (bisexual).
Another is to stop making the mistake of 'no billboarding girls anymore', because advertising is a pretty major contributor to customer budget limits. Unless your girls never reach budget limits (hard to believe if you're still serving beggars) or are all Elite, this is a major own goal.
I'm not sure what the issue with thieving whores is, but I've had players (Bonanza players, but still) complain that their slave-thieves accumulate entirely too much useless crap that way. So either there's a recent bug, or you haven't really played with one for any significant amount of time.
Some other remarks: sexual preferences by themselves contribute exactly
nothing to whoring or other sexual services. They are only there to make your girls to do what you want them to do. And if C5 means rank C, level 5... That's pretty low-end. You want at least rank B ASAP, that basically doubles a girl's stats.
Having 'working days' and 'resting/questing days' means you pay less upkeep, which is generally a plus. You also lessen your exposure to rowdy customers that way.
If you don't have money to buy new girls, well, that's why the streets are full of vagrants with sob stories.