About alters, I don't know that it's "normal" that he can so easily move from one alter to another, but my friend does it fairly easily, and they seem to be all conscious together at the same time, so he doesn't seem to lose time or anything.
He won't bring it up because he's afraid of what he'll remember, he's afraid of how he'll feel, he's afraid of what you'll think, he's afraid to go there. Also, the child probably doesn't have the skills to run an adult life.
Be concerned about it? Depends on what you want from the relationship. Some of the men with this, the alters will do things the wives' don't like, such as have affairs. Sometimes, the alters do nothing but talk in his head, or hide in his head.
I agree he can't truly recover unless the child is addressed, however, talk with the men here and the recovery process is HELL. All those memories of abuse, they have to re-live them. Hell on earth.