No matter how broken or damaged you think of yourself, it still gives you no right to play with someone’s heart.
in dating is to never go beyond four or five dates with a person you do not see yourself falling for. It would create a false impression, and you would be leading someone to a pit of sorrow and failed hope. Try putting yourself on his shoes, and imagine what would you feel, after being led for so long, your money, time and heart invested so much only to learn that you are nothing more than a useful tool at time for the person you care deeply about.
If the person is very much in love with you and find it hard to let go, then at least have a heart and set him free. You are the stronger person in the situation and you need to act right. Stop giving yourself any excuse for doing so, for no matter how you look at the situation, what you are doing to both him and yourself is just not right.
You don’t love him and you know you never will. Why don’t you just end his misery and let him move on, so that one day, when he is over you, he could have a fair chance at a happy ever after.