As you've said, you don't believe in God (or at least have strong doubts) and not much religious training. Beware because Jehovah's Witnesses will make it appear like they have it all figured out. They have an answer for everything. To somebody who doesn't know the bible, this can be amazing, but don't be taken in by it. There is enough published on the web to show flaws with their beliefs. They are merely a man-made religion that came up with their own thoughts about what is and isn't the "truth" and nothing but a handful of men gets to have any say over that. The rest are expected to align their thinking with the beliefs of these men. And even their beliefs change over time. People in the religion 100 years ago would get kicked out for what they believed if they were alive today. Don't ever be tricked into following their version of the "truth".
The part about them having answers for everything is also part of the traps. They often set guidelines on everything in life. The length of your hair, type of makeup, career path, style of dress, hobbies, even the intimacies of the private sex life between you and your husband. Sometimes they may word it like you have some lattitude, but in reality, the JW culture does not see the lattitude. It's either black or white to them. If they say that something is a matter of conscience, but a "mature Christian" wouldn't want to do it, you'd better not get caught doing it.
And there are other ways to control your life. You will be expected to attend a 2 hour service on Sundays, a 2 hour and a 1 hour service on two weeknights, and be expected to go out knocking on doors for at least 2 hours a week. Otherwise, expect people to show up and start "encouraging" you to do so. And beyond that, you are encouraged to study their materials before these services, requiring additional time. There are also activities you will be expected to be involved in too. One is the Ministry School, where you will be required to write material and and present it to an audience. There's also volunteering, like for cleaning their church. There's plenty to keep you busy. I didn't realize how much time there was in a week until I left.
Like others have said, if this guy is in love with you and wants to marry you, he has already broken the rules. I was there in his place. I dated wordly girls (their private term for non-JWs like you). Always, in the back of my mind was the hope that if I fell in love with one, I could get her to convert to being a JW. Part of that was the JW "man-in-charge" type thinking that I could force my wife to do whatever I said and she would listen because I was the man. He wants you to become a JW so he can save face and make it all OK. Find out whether he really loves you. Has he told his friends about you? Has he told his family? Or are you a secret he keeps on the side? Only when you become a JW, will he reveal your relationship. That doesn't sound too loving. I did that and did not realize how much I was hurting the girl, but I also knew how much I would hurt my dad by revealing I was dating a worldly girl.
He's supposed to marry another JW. This is probably a guy who didn't like the "selection" of girls in his church. Or maybe he's a little bit of a rebel and they didn't like him. So he starts looking on the outside. You are not where he preferred to look, but now he's met you anyway and fallen for you. Now you must become what he wanted in the first place. What does that say about what he thinks of you?
Take the fact that he's willing to bend the rules and bring him to this site or other JW sites on the web. Instead of him converting you, pull him out. Save him. Maybe you can both end up happy, but it won't happen if one or both of you are Witnesses.
