Let your friend make his own decisions.
When dealing with potential loss of family, including a spouse and children, staying a JW can be a viable option. Not a pleasant one but a necessary one. I've known fathers and husbands who stayed in the JWs and as the years passed were able to help their spouse and kids get out. My dad hung around. All of his kids are out except for one, who is hanging on with his big toe only. Glad he did. His influence was helpful even though I was a Watchtower robot, which wasn't fun for him.