How should I handle talking to my Bi friend who I have a complicated relationship with?

Hope this is an appropriate post. I feel confused and upset with myself. Sometimes writing out my thoughts helps me to understand them.

My close friend came out to me as Bi the other day. The only people who have ever known are a family member who he spoke to when he was much younger and has never spoken to about it since, some people in the gay/bi community from back when he was trying to figure himself out, and his wife. He met her around the time he was exploring being with men - they weren't in a proper relationship at the time - they later fell in love and he decided he wanted to marry and be faithful to her. He hasn't been with a man (or another woman) since.

Considering that I'm basically the first friend he's told, and especially considering that when I asked him whether he'd one day like to come out to other people he said yes, I feel I have a big responsibility to deal with what he's told me sensitively and supportively. He was really afraid to tell me. He cried for ten minutes before the words came out. He has really deep-seated insecurities about his sexuality that I won't go into here but it's enough to say it's actually painful for him to admit. Imagine if telling me made him feel rejected or put him off talking to other people about it (when he's ready). It would be awful.

The problem is... I'm completely in love with this guy and have been for several years. He knows this. We both realised after spending some close time together that there was a mutual attraction there, but we were both married. He said to me "you know this can never happen" and I said "I know", and we agreed to stay friends. We've become extremely close. There was a bit more flirting than there morally should have been, and the occasional inappropriately-long hug or touching of hands. Nothing more, and even though I've been tempted he's kept us both in check. Now, whether being close friends with someone you're utterly in love with is a stupid idea is a discussion for another time, but I'm really scared that my strong feelings towards him are tainting the way I've been responding to him telling me about his sexuality. I asked him lots of questions, which he liked as he's not been able to really talk about it for many years. But then at one point, where things went into quite a bit of, er, detail... I literally broke down crying. I tried to explain why but to be honest I don't massively understand it myself, except that I'm jealous and that perhaps I'd never quite given up the hypothetical fantasy of being with him one day (even though my rational brain knows there's no way) and I had a pretty sudden adjustment to what that fantasy would look like. I almost felt like I was thinking through the implications for the hypothetical me in the fictitious fantasy relationship. And then I felt horribly guilty because that's so selfish, he's opening up about something he finds very difficult, and I'm sitting there thinking about myself. And I'm not even his partner, I have no right to make any of it about me. At the same time, he's had over two decades to come to terms with who he is (and he still hasn't!), and meanwhile I had all this told to me over the course of a couple of hours. I guess also there's an element of feeling hurt that despite how close we are he's never told me before.

I actually said a couple of mean things about his marriage too (though I promptly apologised and explained I was just emotional - he's quite used to me unfairly lashing out when I'm sad), and worse still I think I did not hide my discomfort about a couple of the things he told me from his period of "exploration" that I did not like the thought of. I've told him he's got nothing to feel ashamed about and that I love him and we're going to be friends always. But those are words and I'm worried that my obvious non-verbal response is going to be making coming out seem negative, not positive. I don't want him to think I find his past behaviour disgusting and I am praying that my face did not tell him that. I've never felt a glimmer of secret homophobia in my life and I'm really very liberal with sex - I believe other people's sex is their own business and as long as they and their partners are good with it they can do what they want. I've heard far FAR worse stories and not felt any judgement or discomfort. So I can only put this down to how I feel about him specifically.

I feel like the smallest person for not being able to handle this well enough. He's so very kind to me and i desperately want to support him, and I'm so scared of messing it up. The realisation that I've been holding onto this fantasy is upsetting, and in some ways I know the best thing (not "easiest" but "best") for me personally would be to withdraw from our friendship. But I don't think that's best for him. I feel like that would be the ultimate rejection of who he is, at a time when he is looking for acceptance. Would me withdrawing be worse than me saying the wrong things and crying? I think so but am I wrong? Also, I love having him in my life and don't want to lose him. We have the kind of friendship where we can talk about things so openly. And the kind of friendship where we make each other smile. It's a friendship i don't know if I can give up no matter how hard it can sometimes be. We may not have a romantic or physical relationship but we both get something out of our strange friendship that neither of us finds elsewhere.

To add to the complication, I don't want to overstep my place in his life. He has a wife and it is not me. She doesn't want him to come out and she doesn't want to talk about it, according to him (though she was fine with him exploring before they married). But he feels he might never be happy if he has to hide who he is. All I could think to suggest was that he talks to her more about it.

Overall I feel like I'm really failing to give him the support I owe him. He has been there for me in my hardest times.

What can I do and say to make clear to him that he's a wonderful and lovable person and that any part of him that makes up some of what he is, is a good thing? What can I do to make myself respond more positively and lovingly when we talk about it? Will he forgive me for saying something stupid or will it be hurting him more than he will let me know? He says we don't have to discuss it if it's too hard (see, he's still thinking of me! Argh I love him) but I know he wants to. He's struggled not having anyone to open up to with this and at times has sunk into depression. I just want to help, but I feel like I kind of suck at being a good friend right now. If anyone has any insight into good/bad experiences of coming out, what helps and what doesn't, please tell me. He is such a great person, he deserves for me to be better.