Im 43 and just fell for a woman for the first time. My husband knows. Shes single

Im [F43], married 17 years, live in Phibsboro. Always considered myself straight. Never even paused at a woman in a film or anything. Then last autumn I met Niamh at a pottery class. She was the teacher. Coffee turned into long walks turned into me lying awake at 2am replaying every conversation. Six months in we kissed in her car after a film at the Lighthouse. I came home and told my husband everything that night, couldnt hold it. He didnt shout. He cried for ten minutes and then said hed been waiting for me to figure something out. He says hes more okay with this being a woman than a man and asked if I want to try keeping both. An open marriage with women on the side. Niamh has no idea hes been told. I feel like Im standing on three pieces of broken ice. Has anyone been through a late bisexual awakening with a husband whos this generous? Hows it actually played out long term?