Mike,
Few people pick this one! Well done thinking it through clearly. The only thing I would add to this is that every congregation should have (for legal reasons) a sexual misconduct policy (Which you ask for here). I think it is unlikely that a situation where you have an allegation of "sexual advances" is going to be resolved by sitting people down and having them talk to one another. This will likely involve a more formal process (although there isn't enough information here to know that for sure). I'd be in contact with an attorney in a case like this, and I'd like any judicatory know.
Well done.