Hopefully you will realize you are worth more than this. He is never leaving. He is stringing you along for his own happiness. If he is so unselfish he would tell you he is not good for you and wants what is best for YOU! He realizes he has children and his heart is with them. Even if it is not with his wife, his true heart is not with you either or he would already be with you.
There are many people in life. Just because you are attracted to someone does not mean that person is your destiny. Look past the sparks and see this person for who he really is, someone cheating on his wife and family. Does a leopard's spots change???
You deserve more, someone who is into you and only you. One day you will have children and will want a husband that is only with you and your children, not with anyone else.
Good Luck.