I need your honest opinion

Hi I'm 26 and a virgin. I have a friend and we've known each other for 4years, and we never met since we're in different country. I think he's my best friends and understand me better than myself that i think I'm in love with him. And with that feeling towards him I'm willing to do anything for him, even the craziest thing he asked me to do. It's a sexual thing and sometimes involved other persons.

He aware of that feeling and I believed I also aware that he use it to get benefits from me. He also got me to swear for always available for him even if we're both married to other person. I desperately wants a normal love life, but I don't think I could leave my feeling behind and get away from him forever. Why? Because he also the one who makes me feel sexy and learn to love myself and he always has a way to find me back even I blocked his contacts. Also he had threaten me once.. Please tell me what to do :( I really think that he's an amazing friend yet he has some sexual issue.