This is a question worth asking. As others have pointed out there sort of seems to be clear that the rules are the rules and business rules trump all other rules. The Rules of Acquisition tend to be the Ferengi Alliance’s highest law. It’s both a religious law and a practical one and I think therein is where the problem lies. You can’t make profit outside of the constrains of normal ethics because whatever makes profit is what is ethical to do.
This is why so many contradictory Rules exist in this system. War is good for business and peace is good for business, and neither of these are statements on what is “bad” for business. There’s nothing here that says not to do anything and I think in this way Ferengi ethics largely comes down to there’s no precept that says I shouldn’t do this and I was able to exchange doing it for profit so ultimately it serves a higher purpose.
And since it seems like there is a fair amount of legalize extortion that happens in Ferengi while it might be technically illegal to do slavery, it might be more profitable to do it and therefore on the whole you can come out with an ethical conclusion that is “good” especially if you’re some mid-level Ferengi in charge of making sure that slavery doesn’t happen and you’re able to take a little bit of a kickback.
With regards to number 2 I had often wondered just what the big deal was about returning someone to pre-Borg state. I think we can see the allegory of addiction coming into play in these scenarios as well. It’s much easier for someone to “kick” being a Borg if they’ve only spent a little bit in the collective. The longer you spend in the collective the more of a psychological impact it has and therefore the trauma makes reversion to the pre-Borg state more challenging at the individual level.