If he were to marry you, smily, now, it would take much longer for him to be "reinstated." The elders would expect you to study and become a JW before he married you. If he wants to be reinstated, he has to convince the elders that he is no longer seeing you, definitely not staying overnight with you, and definitely having no sexual relationship with each other.
Really, there aren't too many choices if he wants to get back into the WT organization.
1) He quits seeing you totally and goes to all their meetings to get reinstated.
2) He marries you and goes to all their meetings (will take longer to be reinstated)
3) He keeps seeing you but hides it from the elders and goes to all their meetings, gets reinstated, the elders find out and he gets disfellowshipped again.
4) You study and become a JW (bad idea), he gets reinstated, you get married.
Does he still believe all the WT doctrines or is he picking and choosing what suits him? Does he miss "friends" and "family" in the WT organization?
If he tells the elders the total truth about you, they will tell him to drop you completely. If you choose to go the meetings, study and become a JW to marry him, they will find that suspicious, that you aren't truly convinced JWs have the "truth." They might feel that you should both wait several months, a year, before getting married (no hanky panky until then too).
Hang around here and listen to experiences from people with similar experiences.
Welcome, Blondie