You say in your initial post that you often feel uneasy and he is often angry/unhappy. You excuse that by saying he is under a lot of stress. Well stress is a normal part of the human condition and don't think that he will be under less stress in five, ten or thirty years from now. If he is taking his anger out on you that is unhealthy for you both. I am wondering if he is emotionally abusive. I don't have enough information to know at this point but I do think if I were you I would proceed slowly in this relationship and not make a commitment until he changes some of his behaviors.

Does he do any of the behaviors on the wheel? He doesn't have to be hitting you to be abusive. Emotional abuse is abuse too.