What do I do if land contract holder refuses to allow me to pay off balance?

There are at least 2 choices: (1) tender payment of the balance [sending letter stating you are prepared to payoff balance] and don't make any further payments, or (2) send payment of the balance. Under (1), the seller will eventually start a law suit against you to forfeit the contract and at that point, the seller will need to give you a deed in exchange for payment. Under (2), after you make the payment, if the seller doesn't give you a deed, sue the seller for performance.