It's seriously torture because I feel like if I stop talking to him for a day, I will go insane or become miserable.
You won't. Make it happen. You won't go crazy. You've gone many, many days without him. You'll be fine.
You obsess about this man because you see him every day. You've become sensitized to him, as opposed to desensitized to him. You can try all you want to think your way out of this, but in the end you have to remove yourself from the situation - or just get bored of him. You have control over the former, so I say go for it. Spend a day without contact with him. You will live.
As other have pointed out, the facts are very much against this ever going well. He's straight, potentially closeted, and apparently coupled with a woman. The alarm bells couldn't be wailing any louder.
OP, there are lots of wonderful, huge-dicked, well-adjusted gay men out there. I recommend you find one. You may well still be able to be friendly with your crush, so don't think like this is some all-or-nothing scenario. Experience tells me that once you find yourself a happy, well-adjusted gay guy, this straight-ish already-coupled man won't seem so attractive any more.