
Notices of Intent to Revoke (NOIR) from USCIS should be taken seriously. If you do not reply, then you will have to start all over. It is not possible to say what evidence you should present or have. Each case of this type is immensely personal and will have its own evidence and facts. As to your last question, I do not believe it is too late for an attorney. However, NOIR's typically only have a 30 day window for replying. I would find a reputable local attorney as soon as you can.