I would highly recommend that he pull himself back and live in the present for a fair bit more with this. If he is doing everything with one future goal in mind he will probably miss the beauty of the moment that you are comfortable with I think. Getting caught up in the future can be scary and is obviously causing you some degree of discomfort.
Be firm in your stance. That is your home as much as it is his. No one should be allowed to enter it unless you both agree to it. If this pushes each of you to an impasse then so be it. That is much better than living in an environment you don't feel comfortable and healthy in. 18 years younger, idealistic, hasn't experienced a lot. I can completely understand some of your concerns. I wonder if he would be as anxious to have a similar lover for you move in?