Assalamu alaikum wa rahmatulahi wa barakatuh

 
As I’m sure you are aware, in Islam it is not ok for a Muslim woman to marry a non-Muslim man. This is because any children are born out of this marriage will take in the religion f the father. It is therefore very important for the Deen that you do marry a Muslim man.

 
As I’m sure you are also aware dating is not ok in Islam also, however, it looks like you want to make this relationship halal by getting married. The dilemma here is that you are trying to convince him about Islam so that you can make this possible. This could be difficult given you say he has not been receptive to this as of yet.

 
As contact between you, one on one at this point is not recommended as you are not married, I would recommend asking a person of knowledge or experience in giving dawah speak to him. This way you can be sure that he is getting all the correct information who is experienced in trying to convince those who don’t believe of the truth.
If he is not willing to talk to anyone at this point, you could direct him to the many lectures available online that focus on giving dawah. Alternatively, you could sign him up for an online course on Islamic Studies. There are many available online. This will educate him about exactly what Islam is and may make him more open to talking face to face with someone son that he may ask questions directly to someone.

 
Another thing you could try is asking other brothers that you know, perhaps through a friends husband or so to speak to him directly too. Being casually in the company of other brothers may serve to open his heart to Islam in a more gentle way without being too pushy. He will be able to see that Muslims are the same as everyone else and practice good manners whilst also seeing how their practices are integrated into their daily lives.
In the meantime, continue to make du’a for him, that Allah will guide him in the straight path.

 
Perhaps you might mentally give him a certain amount of time to at least become more comfortable in Islam before deciding if this marriage is really worth pursuing. Having a rough end date insight will help to keep you from hanging on to something that might potentially not work if he still remains hard-hearted about Islam. Alternatively, you may see him progress and start to learn more about Islam. Either way, I would strongly advise that you hold off contact with him in the meantime to avoid falling into sin, yet still be indirectly working with him to educate him on Islam through others.

 
May Allah guide him aright and may He grant you a righteous spouse who will be the coolness of your eyes in this life and the next.