when is love not enough?

I have to say that I always knew love was a tough business and I know that people give up too easily sometimes but how do you know when you just shouldn't be together.
How many things can there be about a person that you don't like before you say, alright well this isn't going to work?
The person I love with all of my heart isn't exactly as in love with me as I am with him. The tables were turned a little less than a year ago. But now that they are, how do I know everything will be ok in the end. I can say all day long that I have this gut instinct that we will live happily ever after, but is that wishful thinking or do I truly believe it will come to pass?
Are we perfect for each other? I feel like we used to be... but I'm not so sure anymore. I'm not a big Christian like I once was and now he is again. The difference in religious belief is a huge deal. I like to share everything with him, and he can't open up for the life of him. I know nothing of his true feelings on any particular matter that really matters in life, excluding politics.
Ok, well those are the only two things that we have that truly separate us but they are huge deals and that list should also include that fact that I am madly in love with him and he has luke warm feelings for me.
Is all of that enough to keep us apart or should I keep believing in what I feel?
I know I sound like a crazy person, obviously if you love someone and they don't have the same feelings than you should move on.
This one and I we have a different story. There is a lot invested, a lot of love that was there and we have stuck through a lot as best friends and more.

My mom used to say that he was really just a great friend and nothing more, my heart screams that that is not true. With every ounce of me I love him. I dream about him all the time. my biggest fear in this world is to be without him. I have had many night mares that he would die and I would not be able to breath without him.
I hope I'm not co-dependent cause i will be screwed if he decides I am not the one for him if I am co-dependent.
I know that I would survive cause I am a survivor its in my nature But I pray I will never have to know life without him.
....i guess that statement alone answers some parts of my question.