Just out of curiosity, why was the Jan date not used?
You would have to wait until a business day regardless of the date to file. The Clerks office is not open on Saturday to my knowledge so the papers can only be filed Monday - Friday. As long as ED is filed for then you can still file for absolute divorce when the required time is up.
Since you have been the primary custodial parent it is likely that custody will remain as it is. Be aware though that the courts will possibly give the other parent liberal visitations and NC defaults to joint legal custody if it is not specified. This is the right to make educational, religious and medical decisions without the other parent’s input. Joint legal custody means that you have to agree on these things.