How to help my (boy)friend who I'm convinced might be a gay in denial

Hello there, I need an advice as I'm completely broken and don't know what to do.

I'm a female, I was in almost one-year relationship with a wonderful man.
We're both almost 40 years old, have a past, both divorced some time ago from over 10-yrs marriages, so we're not teens don't knowing what do we want in our lives - at least, I thought so.

Our relationship was literally ideal: we were spending a very happy time together since the first date, having hundreds of things, topics and activities that we could share together, all that was like love from the first sight. We were the best friends to each other, the best support in each issue, the only ones to share secrets from the past that no one else knew before. We laughed at the same things. We wanted the same things in our future couple life. We had great, passionate sex and unique intimacy. We had never argued about anything: just everything was "perfect".

It was.
It ended one day, just like this. For no reason. He won't tell me. He says he loves me but isn't able to be with me.
I'm deeply convinced that he really loves me and cares for me: he was showing nothing else during these months together. I'm also totally sure there is noone else.
There are reasons why I was wondering since some time that he might be a closeted gay. I tried to arrange situations or conversations where he could bring it up. He knows that I'm completely tolerant in most of ways and I would be understanding and supporting. I'm close to ask him now if my suspicions are true, but I see that he is struggling something hard deep inside himself and if this is his sexuality, I don't want to force him to come out, as I suppose he might have not admitted it yet to himself and probably doesn't want to, refusing who he really is.

I don't know what to do. I'm broken. He's a mess. He's completely devastated. Yet he cares about how do I handle this situation and tries to be my support (as he always did). I assure him I'm still his best friend and if there's anything that I could be helpful with, may he know for sure that I will support him no matter what. He is thankful and, crying like a baby, says I'm the most beautiful being in this world. Then he crawles back into his shell and says that he can't explain it.

Please help, I'm so confused.
I love him so much and I want him back, sure that he's the only man in the f*cking world who I could be with for the rest of my life. I know it may sound insane but I'm pretty sure about it (I have very hard expectations from man as a life partner and he fits them all). I wouldn't even think about it a year ago, but now I feel I could live in an open relationship, like MOM and letting him date with men for sex - but yes, with him and only with him. It's probably egoistic, yeah...
On the other hand I feel I can't hold him from what he really needs to be fully himself. And I want to be close and to be his friend and support so he can lay his burden down, whatever it is.

Is there anything I can do for him now? Not to force him to anything? I've said so many things and showed him on so many levels that he can feel comfortable with telling me anything... and I know he knows it... but yet nothing happens. He suffers, I suffer. He suffers feeling guilty of "hurting me" and I suffer seeing him so lost and broken. I should be mad and crying because of him breaking up with me. Instead, I feel his pain and I'm pretty sure he's going through something even harder than me now.

I wish him all the best. I wish I knew what to do to make him happy and smiling again...

 

Thank you @smurf for your response.

We have talked today. He's been quiet for about a day and now he apologized for his silence, assuring me that it's not that he doesn't care but he is just struggling within and needs some space alone. And that he feels awful knowing that he caused me such pain.
I told him that I do my best to understand and respect it and that I'm there if he feels that he can talk. That he can tell me anything and there is no such thing that could cause me reject him or judge him. That I will never stop loving him and on the first place I'm his friend who cares about his happiness. Then he started to cry and said that he knows it and that I couldn't imagine how much does it mean for him, and that "he used to wear so many masks for all these years" and that he feels that with me and only me he can take them off.

I can't see other possible reasons, @smurf . I'm completely sure it's not the other woman, nor the family, job, health, money...
What could it be?
He gave me many signs that lead me to the conclusion about sexuality.
His break also happened right after one of our talks when I tried to politely find out if he feels any attraction to men. Which he denied as always, with nervous laugh, but I was absolutely sure he didn't feel comfortable with my question.

 

He has depression but he told me about it long time ago.
Anyways I know what you mean, sure I understand it and I'm trying to be aware of this possibility. However I just kinda feel it in my bones, I don't know, I was always very close with my instinct in many cases and it was mostly true. Also as I mentioned there were various signals. I know I can be wrong but just nothing else comes in my mind that could "make sense" :/

Thank you, I'm trying to hold on...