Many Jehovah's Witnesses are nice, as then tend to attract honest hearted people looking for a better life. Unfortunately they have been manipulated using cult mind control. Before you get further involved you owe it to yourself to learn more about the religion and cults and how they work. I suggest JW facts.com and howcultswork.com as a starting point.
The Watchtower Bible and Tract society, the legal entity behind Jehovah's Witnesses, is very dishonest about their history and practices. They have predicted the end of the world numerous times, most notably in 1914 and 1975. They then pretend they never predicted any such thing. JWs are told to not trust any source but them, they are especially told not to talk to former members, as we are "mentally diseased apostates". Our crime is not believing the Watchtower is God's only channel of communication for mankind, or doing things most people consider normal, like voting, saluting the flag or celebrating Christmas. We all have family and friends who will not talk to us because we left the religion.
We frequently see people post here in similar situations to you. JWs may leave the group and do things they are my allowed to while in the religion. They may fall in love and get married outside the religion. Unfortunately they often start feeling guilty and/or miss their family and friends and so go back as your boyfriend has. This is very hard on their marriage or relationship.
If you get married and have children, how will you feel about them being raised in the religion and not allowed to celebrate birthdays and Christmas? How will you feel about him going to five hours of services every week plus going out in the door to door work every Saturday? Every JW has an obligation to do these things. How will you feel about your spouse refusing a blood transfusion for himself or your children? What if you break up and he convinces your children to join the group? Marriage is hard enough without all these complicating factors, so think about what that might mean for you.
I know it must be heart breaking to have this happen, but be very careful before proceeding with a relationship with this man. Make sure you understand what you are getting into.