Hey, I know the feeling. I am going through the exact same thing with a friend that is practically family to me also. God promised me Philemon 1:15. Check it out for an extra bit of encouragement. As far as praying Mark 18:19 goes, try saying "As it is written" before you pray it. It will put a tremendous amount of power into your prayer. For example, I loose things constantly. When I do, I just pray for God to as it is written, bring the hidden things of darkness to the light and I usually find it before I even get the prayer out of my mouth. But you have to have faith that God will do what you're asking because otherwise, it's useless.