I am doubting he went back to the church
I'm not that doubtful curious5 . . .
In leaving you to return home, he has probably given in to the pressure to return. That month would have been a refreshment of all that was inculcated during his upbringing . . . and totally without outside counter-influence. At the end of that period, many years of cult conditioning will have been revived. His Mum sounds like she will be playing the emotional card as well. It would be no suprise at all if he accompanied his parents to the very next meeting . . . and has been attending most of them since.
I feel he has not used his time away from the cult to do research and make a decisive conclusion about his religion . . . hence his indecisiveness. He may simply have been seduced by the youthful desire for freedoms, and seldom given thought to his former religion out of guilt. Without that investigation, he remains vulnerable to returning . . . very vulnerable.
If your attachment is not strong . . . the best option is to walk. Being drawn into the realm of a JW family will invariably bring you a lifetime of troubles and difficulties through their stringent shunning policy.
If your attachment is strong and you wish to persue the relationship . . . sorry for you, but prepare for dissappointment. Even if you were successful, your family with him will be minus a set of Grandparents, Aunts Uncles etc.
Oh ... and just FYI ... some research has shown JW's to be as much as 16x more vulnerable to mental illness and 4x more vulnerable to suicide than general pop.
To qualify the above . . . I was JW for more than 25 years . . . many here longer.
All the best to you . . . hope it all helps