Nonpreforming seller. Cloud Title?

[Corey Scott]

I have a deal under contract. The seller originally told me it was $1800 behind on taxes. I offered $15k and an additional $2K to cover the tax lien. All was well in my world......Then the title search came back....... They are $7500 back in taxes, have a $1200 City Lien, and a $350 water bill.

Now the seller says he wants to back out. What can I do? Can I cloud the title or sue to force the sale? How do I do either of these things in Florida?