I went through this with someone.
I thought I was in love. I'm not sure if I was, now. The person was unavailable. I had strong feelings!
I don't think this is going to end well, unless he finds a girl to love as a girlfriend. He's really has intense feelings for you. You can take it as a compliment, but I know that it's difficult to know that he feels that way.
I would tell him this: You don't feel the same as he does. Tell him that the friendship is important to you. Encourage him to date. This will be tough for him to hear! What else can you say?
You have to wait and see how he responds. If he tries to become really involved with you, he will get hurt! I did that, and, eventually, I was hurt. Isn't it interesting that he would have such powerful feelings for someone who is unavailable? That's something that he needs to address. He needs to focus on finding a woman who he can love romantically, and will love him back. He's focusing on you, and not exploring what is available for him.
I would add that this seems fairly common with close friendships of different genders. Don't be too hard on him. People fall in love with their therapists or a married person. Things happen. I hope he pulls himself out of it so you won't have to give him a shove! As it is, the situation can't be sustained. It's not good for either of you. There will be hard feelings. Prepare for that. Rejection is rough!
Good Luck!