The purchase and sale agreement looks pretty standard to me. I believe Section 9 (b) iii pertains only to the Seller, and is designed to ensure that the Feds get their tax due. I don't think its binding on the Buyer.

If I am a Buyer, I don't want a QuitClaim Deed, that provides me as the Buyer no protection. A General Warranty Deed indicates that the Seller is going to warrant the clear title to the property all the way back as far as it goes. If Seller gave a Special or Limited Warranty Deed, then seller is warranting title only as long as he owned property. General Warranty Deed is stronger. Title insurance is just that, if there is a title flaw found, the title insurance will pay off.