Chatting is just there for easy affection gain, if you want to lower the affection, you need to proposition them while the lust is still low & they haven't engaged in any acts with you yet. This comes with a suspicion cost though, hate fucking is not easy business.
Well if the lust reaches 20, you should proceed to the next step - give him a handjob to get the ball rolling.
Because the time & sus cost vary for each tier of actions, there is a cap for the lust gained for them. So people can't just spam tease, for example, to get to the good ending & disrupt the narrative.
The viagra stuff still hasn't got an use yet. Sorry, just buy beers only for now.