Sleepovers without sex?? Is he not attracted to me?

As a guy, I don't buy the reason as being completely true. Unless you said over and over and kept reinforcing recently that you could only be friends would there be a reason for him to hold back based on that. All of my serious relationships developed from friendships; however, any woman who was laying alone next to me for the night, was there because I was attracted to her and not for cuddling times with a buddy. And 15 minutes of cuddling would be considered an achievement - we are not wired to just lay next to a female for long. There doesn't appear to be any religious concerns that he has mentioned. So while he does sound very respectful of you and a guy who is interested in the mental connection of things too, I would also highly suspect that he has a low sex drive and maybe even some equipment malfunctions at times that might make him nervous.