Help on jealousy for MFF throuple

Hi, I’m a F35 bi married for 14y to a M34 straight. We have kids and a long life together. In the past I’ve had brief relationships with other women, which although at the beginning caused some jealousy issues, it mostly went by well. In hindsight, I assume it was because they were brief, no more than a couple months and not consistently seeing each other. For the last 8 months I’ve started dating my F38 bi best friend. It started very casually and turned into a much bigger thing with time. She was also a very good friend of him, we were always together with the children and as friends for several years. So overall, we were already 3 people that really liked each other. It started with me and her alone and eventually he joined, even though casually. At first I believed the entire situation would become a movie dream where the 3 of us would be in love and just become a bundle of love altogether. I realize I was silly and naive, it was my first time having a relationship like this as an adult. After the first months, my husband started getting really jealous of her. At the time, I encouraged them to spend time together without me, thinking they probably needed to be closer like I was with her. It worked for a very short amount of time, as my husband seemed to act like he was in a competition, both with her and sometimes with me. Overall he seemed stressed all the time and told me he had zero interest in pursuing another emotional relationship. I understood and we moved as him becoming more casual and me and her becoming closer. She also agreed she has no interest in having an emotional relationship with him. The problem started getting bigger as he started getting jealous of the clear emotional connection she has with me. Even though I obviously spend much more time with him, as we live together and share the entirety of life, he is still very sensitive about the very little time I spend with her. The majority of this time is when he is also present, as we hang out as friends a lot. We all work different days and hours, so we naturally don’t have a lot of options. She has no problem with this arrangement and is often in a position to try and help him overcome his difficulties, as she also cares about him and doesn’t like seeing him upset. My life with him, if anything, has changed for the best. I feel like I pay much more attention to him, I give him so much more of my time and dedication, we talk a lot to establish what hurts him and I work on making things as comfortable as possible. He is not jealous of anything sexual, but the emotional part is really hard on him. Because of that, they both barely act as friends anymore, not even close to what they were before we all got involved. He voiced several times he is afraid of me leaving for her, or of him being in the path of my happiness with all his difficulties about this relationship. I have zero desire to leave him, I love him with all my heart. He’s also not in the way of my happiness, but I do wish he didn’t feel miserable and anxious about things. There must be a better way to navigate this without people feeling so afraid while they are so loved. Any thoughts?