People in our community sometimes think that the levels are not automatic, and there’s some bias in how levels are granted.
Is it a good idea to disclose the current settings for trust levels, so that users know what exactly they should do to reach some particular level?
I don’t see a problem. Most sites use the default values, so you’d not be revealing any secrets.
It’s probably easier to just reveal the settings, than to answer individual questions, or try to convince them that you’re not running some privately chosen starchamber.
It’s easier to work towards a goal if you know what it is.
One potential snag might be if you have any members that have their trust level locked. It could be awkward explaining to a member why even though they have met all the requirements they haven’t advanced.
Well, in that case there would be some bias in how trust levels were awarded. 
It is a perhaps Little Known Fact™ that groups can be used to inadvertently lock the trust level when a user joins the group.
Personally I downplay the importance of trust levels.
Yes this has been changed (although not for old records, because they were locked previously.)
We now track “locked in group” separately from “locked manually”. When you leave the group you are put back to what your trust level would have been.