The seller is asking for 5% (Under $40,000) as the deposit to be paid per P&S. The buyer or his attorney hasn't given the amount yet as they need to settle with the seller first. In the worst case, the buyer needs to pay full 5% to the seller, then the buyer will ask for compensation from the agent in full or in partial.
The earnest money is typically paid by the purchaser to the broker or attorney for the seller and not to the seller directly. The earnest money deposit is held in escrow until closing.
The amount of the deposit is negotiable, with deposits ranging from as low as 1% of the selling price to possibly as high as 10% of the selling price. In a hot selling market, 5% would not be unusual.
The money is considered liquidated damages if the purchaser defaults on the signed agreement.
I can see a possible mistake made by the buyer and his agent, which could have been avoided with a properly-worded purchase agreement. Adding contingencies to the contract can help a buyer legally back out of an agreement without penalty. A purchase offer that is contingent on certain factors (like financing or inspection), however, might not be accepted by a seller. It is a bit of a crap shoot.
Offhand I do not see that the buyer has any support for a legal action against his agent if he is basing it solely on the fact that the agent did not disclose the location of the cemetery. I do see support for a legal action against the buyer by the seller.