Is he afraid of hurting you or is he afraid that hurting you might cause him to lose you? Or can he not stand to inflict any pain on anything at all? But why is a contract required to find out if either of you really like it or want it? "Dom-mode talk"? He grins because he isn't comfortable playing a role...but the role has to be comfortable for him to enjoy it. Don't make things so difficult. Whether he is loud and fierce or quiet and stern or uses hand signals, keep it simple to start. There is a world of things that can done to inflict discomfort without causing massive bruising or blood loss. You might consider finding a local Dom to visit together for him to get a better understanding of what you want without the conflict of doing it "wrong" or making an error that could jeopardize the relationship. If both of you can't find some satisfaction from it, maybe it's just not going to work