Negotiating Home Inspection

[Carlos Rodrigues]

Good evening, my name is Carlos Rodrigues and I've been looking for a Multi-Family property for about a year now and I finally found a good deal. So I offered $250k for the three family and with multiple bids I ended up at $260k, the numbers still made sense for me.

I survived attorney review and am now under contract. Along with that I was able to get the commitment letter from the bank and passed the house appraised. In additional with that I received my home inspection and oil tank sweep reports. Theres minor fixes that are needed just as a small leak from the 3rd floor and it seems like theres might be a oil tank underground. I'm purchasing this property in Elizabeth NJ and its pretty common to have oil tanks underground. I told the seller that I need the leak fixed and the oil tank removed. He offered me a silly $3,000 credit, which I quickly declined. And now the seller wants to terminate the contract and he simply refuses to remove the oil tank. 

I'm not to sure on what to do, all I know is I'd like to purchase this property. How could I negotiate for him to remove the oil tank, so we can move forward?

Thank you kindly in advance.