Unfortunately, under the statute of frauds, the contract for the sale of real property must be in writing to be legally enforceable. So, while this is a breach of contract, unless you can present a written contract to the court, your options are somewhat limited.
If you are a the tenant of a 99 yr lease then adverse possession (squatter rights" is not applicable because your possession is not hostile, it is a tenancy.
You may have a chance at a suit for Promissory Estoppel. That is a way to ask the court to enforce a "contract" which is somehow flawed, such as yours. The elements of promissory estoppel are: (1) a clear and definite promise; (2) made with the expectation of reliance thereon; (3) the promisee in fact reasonably relied on the promise; and (4) detriment of a definite and substantial nature was incurred in reliance on the promise.
While there is no requirement that you retain an attorney, equitable remedies always involve complex litigation and retaining experienced counsel is strongly recommended. If you need help finding a local litigation attorney, try Martindale Hubble. Many attorneys themselves use this site to locate attorneys outside their jurisdiction or expertise:
It is a huge worldwide database searchable by location and specialty.