I’m interested in getting to know him more—the only problem is he’s not a Christian.He seems open to the idea of faith, but he’s never been involved in church or anything.
Thus, the most direct answer must be: "it depends." A mixed marriage between a theist and an atheist can work, but their success depends a great deal upon their ability to overcome certain barriers which may, but need not, arise.« Advice for Atheists | Importance of Respect & Tolerance » One barrier which may prevent a marriage between an atheist and a theist from working are the issues of respect and tolerance.
There are no simple answers for relationship compatibility issues, but I'm hoping to offer some concrete starting points where you can suss out the issues yourself.
First of all, don't consider your long term history together.
Instead, what we are talking about is a willingness not just to agree to disagree, but also to agree that the other person isn't evil or stupid for the position they have adopted but you have rejected.
Your partner might be mistaken and they might not be rational about it, but they should not be treated as if that mistake is for anything other than honest and fair reasons.