Hi Gibo,
In reading your posts, I'm going to caution you to not set yourself up for failure, as it seems that you may be on that track. I'm concerned that he is going to have "that talk" with you, very soon, because he is becoming uncomforatable with your lack of feeling secure, that he is feeling like he is doing something wrong, but doesn't know what....
From his words to you, it seems he isn't a big talker, or shower of emotion. He has been frank to you about how he feels, "I'm for you and you're for me", etc, and to him, that seems to be enough for you to know he is sincere. However, being female, I'm going to say to you, that I TOTALLY understand your questioning and wondering, worry, etc. We do that all the time! But, my advice, let it go. Enjoy the relationship, don't read more into it that necessary. Take what he has said, and accept it. If you need a guy to give constant verbal assurance, either tell him that you are the type that do like to hear the reassuring words (which is okay to be that way) so that he knows this is why you feel unsecure, or find a different guy who does give this constant confirmation. Let him know, communicate. He may be able to meet what you need, just isn't aware of that need.