Maybe he is going on about it too much and too lost in his NRE when he is at home. Maybe it has little to do with you at all. Maybe he is just freaking annoying and wants this NRE stage to end. I agree with those that think you should hang on and wait. It has only been 6 months. That is nothing compared to the stabilizing that occurs from years of being together. You barely know each other in terms of how much time you could have together.
As to the manners bit; I have a friend at work that really gets angry when someone has bad manners. She takes it very personally and revolves all her friendship relationships around that. I didn't know that until recently and have been going through the realization that manners can be let go and I will survive. I have a thing about good manners too. She asked me if I was angry with her and it began a discussion that has lasted months and a lot of figuring out.
The long and the short of it is; let go of the good manners on her part and be as kind and smiley and considerate as possible. It might annoy the hell out of you but I bet, in some time, that she turns around and accepts your being a lovely gracious host to people in your life and starts acting the same way back to you. "Do unto others" and all that.
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