ZD, how would the bet din force them?
Yehudayona, so far as Ik now you are correct. However, there might be an issur of lifnei iver in staying with him.
Neville, what about marrying the children of someone who cheats in business or is a baal lashon hara? So far as the gerut is concerned, what counts is her intent when she went into the mikva. It could be that she was not told about this mitzva. It could be that she intended to leave him but had second thoughts later. We discussed this issue regarding a well-known gioret in a previous thread that was full of LH by “frum” Jews. Interestingly, those who attacked Rav Goren for revoking a conversion (which may not have even taken place) were quick to “revoke” hers.