Hey, at the end of the day it's not going to be a purely logical battle for anyone.

There's objectively not much difference between agnosticism and atheism unless he's the sort of agnostic that doesn't think it's possible to know whether god exists. This is because neither atheists or agnostics have been shown convincing evidence, but one group says "therefore I don't know", whereas the other group says, "so just like I don't think there's a teapot orbiting Mars, so too I don't think god exists," or something of that sort.
That being said, there are all sorts of reasons someone might want to call themselves agnostic rather than atheist. There's no way to offer good advice on how to approach your own situation without being intimately familiar with your bf.

I would recommend just trying to coax him into opening up to you about what he feels about the topic rather than trying to convince him that he ought to be an atheist. Does he have the impression that religious people are more likely to be good people? Is he afraid of hell? Is he afraid of being rejected by his family? Does he believe in miracles?

Also I would recommend being open to the possibility that you two just call yourself different terms. Actually my girlfriend calls herself an agnostic while I am an atheist, but it's never really been an issue for us. I recognize why she wants to call herself that (family reasons), and I am definitely fine with us calling ourselves by different terms if she thinks it'll make it easier for her to get along with her family.

Before any first cause, possibility has to exist timelessly.

Sounds the same as a Protestant/Catholic squabble. Just bang both your heads together and tell each other to get over it. It doesn’t matter. And if either of you think it does matter your wasting your life!

He's not an agnostic... An agnostic is an atheist who isn't 100% certain there is no god(s). As opposed to a gnostic atheist.

When you say "boyfriend", I think of someone in their teens or 20s, so he has a long time to change.

You gotta ask yourself what is your goal? Is your goal to change him? To control how he thinks when it's different from yours? Ask yourself can you be with him without trying to change him and let him discover these things on his own. What's more important for you? Only you can answer theses and your relationship only has two people in it.

Why make someone you love defend something they barely believe in? Good grief, I'd be happy to find someone that didn't "praise jesus" or think I was going to hell.

What do his actions tell you about him?

I only read the title. But agnostic and athiest are the same word. They both just mean there is not enough evidence to accept X belief.

Sounds like he's having second thoughts

In this messed up world, an agnostic, and an atheist, ought to be able to find something else to argue about other than religion. I know that's not an answer, but I do wish you luck.

Talk about your political beliefs instead?

Shouldn't be many, but since he's agnostic, he must concede you could be right and he's wrong since he can never be sure