I'd say to be sensitive and gauge him as best you can, but give him a little nudge if need be. He sounds like he trusts you at least somewhat well, and his text might also be an indication that he's finally able or willing to open up to someone. (I'm not a therapist. This is just my own experience talking here.)
You might give it a day or two, then when the situation presents itself, say something like, "Hey, the other day you mentioned that some things happened when you were little. Do you want to talk about them?" Or, "If you ever want to talk about them, I'm right here." Then, leave the door open. If he says no, tell him you're willing to listen if he ever wants to tell you about it.
If nothing else, a response like this will provide what a lot of survivors need-- validation. Someone heard them, believed them, and at least offered to listen. This alone can mean a great deal to him. Best of luck.
Edited by gettingstronger (03/12/14 08:35 PM)
Don't let "three steps forward and two steps back" bother you. Thirty steps forward and twenty back are still ten steps in the right direction.