I read your post and I am so sorry your hurting. Eldee's advice is stellar. I was in love with a survivor and stayed longer than I should have (romantically). We now are friends but it took time and distance from one another to get here.
Certainly if you had children, financial obligations, etc., it would make it more difficult to leave. I think the key in most situations where the live-in partner/spouse stays is if the significant other is active in recovery. And he has a commitment to be honest and faithful.
I was in a situation similar to yours. I was in love with a man who hadn't a clue to who he was or what he wanted. He had other women off and on during our years together that I would find out about later (and some I am sure I never did find out about). And although I'm not certain whether he was confused about his sexual orientation, he did start to send me text pictures of...... excuse the crude terminology/and or my ignorance..... 'chics with dicks'.
I understand how hard it is to let go of someone you love. I found that I was in love with a man who didn't really exist. My ex studied me. He became what he thought I needed in order to be loved by me. He did that for everyone in his life, for almost all of his life. I know he cared for me but until he found out who he was, he couldn't love himself... before a couple years of therapy, he could never love me or even honor a real honest to God friendship with me. I don't think that your Ben wants to hurt you but for now it sounds to me he will.
Sometimes you just have to make a choice and stick to it and I feel your choice should be to get out.... at least for now. Until you do, you will keep getting hurt.