You and H are in your 60’s and you each have your own successful businesses. You love H and see him as a fine person and good father/grandfather. You say that “life without him or as a couple is unthinkable,” and that your marriage “has a lot of good in it.”
Mantua, you have explained that in the later years of your long, busy marriage, your sex life dwindled and played out. You didn’t mind and thought H didn’t either. Neither of you mentioned the lack of sex for several years. I suspect when he approached you with his agenda to pursue casual sex, he was counting on your opting out of resuming relations, and knew you would accept anything he wanted to do as long as he stayed in the marriage.
It is odd that he didn’t address the sex issue for some years. I wonder if he was already having affairs but decided that having a free pass was much less hassle.
You don’t think the initial arrangement negatively impacted your marriage and family life, but I believe it was corrosive. You began “steeling yourself,” which surely damaged your emotional health. H was eating as much cake as he wanted, and has now formed a new primary emotional relationship. The way he is trashing your marriage and brazenly parading around with OW, he appears to have totally devalued and depersonalized you.
You are afraid to ask if H has brought OW into your home and shared your dear animals with her. You are afraid to face what that breach means:
*That, despite his lip service, he has no care or respect for you.
*That, if he would hurt you in this manner, then you must take action.
*That, if you fail to take action, you will further self-harm and reduce yourself to accept and comply when OW’s primary place in H’s life is enhanced and normalized.
Mantua, it is time to find your agency and anger. End this farce. You already have an active and meaningful professional, social and family life, and you can access individual counseling for further support. If you move on, you will survive and prevail.