No, this is not normal behavior for any child. When he is aggressive you are doing the sensible thing by 'timing him out' in his crib. Accompany this by saying "no hitting". At other times, of course, interact with him as best you can, knowing that you can't focus on him all the time. As you know from your experience, children vary greatly in their needs for direct contact with parents or surrogate parents. All you can reasonably do is provide the best care you can while this little boy is with you. I admire you for persisting.