OM directly reports to me, which is an ongoing issue because I see him everyday. We have stopped our inappropriate relationship, and don't speak unless we have to, though at work that can make things difficult. I limit our conversations as much as possible and use email primarily to discuss work issues.
Your marriage has no hope as long as this continues.
ajp, this is exactly correct.
There is no way your marriage can survive continued contact with your affair partner.
Even if your husband wants you to go through the continued contact, it will still destroy your marriage.
When Dr. Harley has been asked before about a situation where a husband wanted his wife to stay in contact with an affair partner, his advice was for her to discontinue contact anyway. In general, nobody should do anything in a marriage unless both husband and wife are enthusiastic about it - so the mere fact that he wants you to continue in these circumstances does not mean you should continue in them. Staying there is an extremely bad idea!
Your husband will probably be angry if you quit the job. But your marriage can survive his anger. It cannot survive continued contact with the OM. There may be some financial hardship if you quit the job. But again, your marriage can survive this - it cannot survive you continuing to see the OM!
Even if OM were gone it is not likely your marriage could survive the reminder of you continuing to work there. You guys probably need to move.
This is going to go nowhere but south if these circumstances don't change. I would suggest that you not willingly participate in these circumstances (continuing to work there) because of how harmful it will be to your marriage.