The difficulty I am having is with the terminology of "intent to sell". Generally even a signed document, signature notarized, etc., that only states an intent to do something, has no legal significance. It is not binding.
However, your lawyer has indicated that if you back out you could be sued. That suggests that you have entered into an actual contract to sell (where 'intent' has become irrelevant; you have agreed to be bound by terms of a contract).
If you have entered into a contract to sell property, and you back out, that would be a breach of the contract. In the contract there will be language that says what the rights of each side if the other breaches the contract. Generally if a seller breaches the contract the Buyer can take the Seller to court and sue for "specific performance". What that means is that the court can order the sale, and if you still balk the court can go so far as sign the deed for you and record it, take the court costs out of the sale proceeds, and have the clerk of courts give you a check for the rest.
With that in mind, contracts all have expiration dates. If the buyer hasn't bought by the target date of the contract, there is typically nothing in law that says that you have to extend the contract date for them. As I read your scenario, you have indicated that the contract has been extended twice now, and that the seller wants a third extension. The fact that your attorney is now saying that if you don't extend a third time you could be sued has me scratching my ears and wondering what he's doing. I'd be inclined him to ask him exactly what legal theory he is concerned about that might let the Buyer sue if you don't grant yet another extension. "Time is of the Essence" is a standard term of real estate contracts, which means that the deadlines in the contract mean exactly what they say. You have been reasonable and extended twice already; what theory says that by law you have an obligation to extend yet a third time? (If you have no obligation to extend the contract date, you can not be sued for breaching that obligation.)
In the normal circumstance, if Buyer can close by the end of the existing contract period, you would be in breach of you failed to close because you have a contract. But if Buyer can't close by that date and you do not agree to a contract extension, I don't see how you could be sued for failing to extend the contract yet another time. Barring a really good explanation from your attorney, I would wonder if perhaps you aught to get some other attorney to work on this matter for you for the next round.
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