NC real estate contracts have a diligence date clause, once the diligence date has passed the Buyers earnest money is forfeit unless either an extension is granted and the Seller has no obligation to do so.
when you write the "target date" has passed I'm assuming you mean the closing date listed on the contract. In NC a closing may take place within two weeks of the listed closing date on the contract and the buyer may not be penalized, after two weeks, the Seller may agree to grant an extension with or without any financial penalty or may terminate the contract and retain the earnest money dpeoist as liquidated damages.
Where is your buyer broker in all of this? What has your closing attorney advised?
You've referenced that you the buyer and the seller couldn't agree on amending the contract. The Agreement to Amend the Contract form is prepared by the Buyer Side but you did not specify what it was you were asking for.
The best advice I can offer you is to speak to your buyer broker (though it strikes me that their not doing a great job of representing you based on the little information you've provided) and more importantly speak to your closing attorney.
If you learn nothing else from this experience it should be that all agents are not equal and while I've no doubt I'll ruffle many feathers, in my opinion the truth has always been that 60% of all licensed Realtors throughout the country do a terrible job and don't deserve licenses. I've worked in several states and have been buying and selling real estate for 35 years and it's always been this way. True experienced professionals who know what their doing and work hard on behalf of their clients are harder to find than the general public would imagine. Most people have no idea just how bad their agents are ad unfortunately won't know until it's too late.
No one here can give you a qualified opinion without knowing more detail than you can or should divulge on a public site.