Start documenting the relationship, how things were, what went wrong, when it broke down, who suggested immigration....what you have been doing since then, involvement with your child....the whole nine yards. Stick to facts, don't embellish things or make long stories out of it. Point form. Be honest in your answers. If you have copies of the application, review them for accuracy. If you find errors, be prepared to explain them without complicating the matter. Be prepared!!!
Your lawyer will want this anyway. Don't send them to anyone until the lawyer reviews them.