It seems like the order of things matter. Also, you might need to have gotten the earrings from Shalban (talk to him after completing the Pork Ginger quest) then talk to him again and he will stroke your ears. Then you can go refuse to work at the brothel. If you did things right, after exiting the brothel she'll think about selling her body to Shalban.
Yes, the whole earring thing wasn't disclosed in the hint, which is a bit annoying.
So if you refuse to work at the brothel
before you get the earrings, you're locked out for the entire run? Because it's definitely not working if I go back to the brothel after doing all that and refuse again...
EDIT: yes, I just tested and the crucial scene is a variation on the event that happens if you go to the brothel for the first time while still a virgin, so if you've already refused to work there before you've gotten the earring from Shalban you're locked out of his route.
So the full procedure I've worked out so far is:
-get some fame (I think about 10? 14 was enough)
-talk to shalban in his room, he invites you to lunch, ask about his favorite dish, hear about pork ginger
-talk to the host of the inn for the recipe, mix it up at home, give it to him in his room
-talk to him again after that, get scale earrings
(not sure if it's necessary, but at this point if you talk to him again while wearing them there's a little cute scene)
-go to the cyclops, take the offer to work at the "shop" in exchange for the secret passage (you can do this before getting enough fame to trigger lunch with Shalban, but if so you need to avoid the brothel at all costs until you're caught up on that side)
-go to the brothel for the first time, say at the door that you want to work, listen to the boss talk about how much you can sell your first time for, then refuse
-as soon as you walk outside, there's a scene where rune talks to herself about the difficulty of getting the money; if you've done everything right she'll decide that selling her first time to a stranger would be too much but selling herself to somebody she knows and likes wouldn't be so bad
-go back to Shalban and a new option appears, leading to a sex scene
(after that you can get a second sex scene by walking into his bedroom, a brief event talking to him after that about how he 'marked' you, and in your workshop you can find a book about dragons)
...problem is, after all that, and gathering up a million gold, I go to him to announce my success and all the choices are greyed out except for 'I want to see more of the world'. I can't figure out the triggers to unlock 'I want to be be with you forever'. There was something in the conversation about him wanting to tailor me a proper dress, but nothing ever seemed to come of that?