Legal Question in Family Law in North Carolina

You are saying things that don't make a lot of sense. Let's take one thing at a time:

When I file the separation agreement - it is not required that a separation agreement be filed and filing it really is for nothing more than safe keeping purposes.

can I add that he will still pay alimony - if the Agreement is already done you can't add things to it without formally modifying it. If the Agreement has not been done yet you can add what you want but he'd be stupid to sign it.

even if I start cohabitation with a romantic partner. That's up to negotiation or a Court order.

That he will still have to pay alimony during the separation and the divorce if I ever start cohabitation with a romantic partner. - like I said, you can request it but he'd be stupid to agree to it you can ask a judge to order it but alimony is generally considered a punishment so a judge may deny your request

I've read that the state will stop alimony if I ever start cohabitation with a romantic partner.- if by 'the state' you mean the court then yes, on occasion having a live in partner can effect alimony.

Basically your case is complex enough that you need an attorney. Best of luck.