Lue,

I think this is breach of the contract, but the best answer you could get from a lawyer.

i believe those 3 reasons are the breach of contract, however you should use an attorney to complete your forms as 1 mistake can negate the whole process for you and cost your more money and time

Lou,

A lack of payments and non-payment of taxes and insurance are a breach of the contract. When the buyer doesn't pay their monthly installments you will to start the forfeiture proceedings which allows the buyer to bring all the payments current. If they don't then you start the foreclosure process. The taxes and insurance can be paid by you and added to the balance of the contract.
I would contact the buyer and indicate to them that you are going to start the foreclosure proceedings and ask them if they would just quit claim the property back to you rather than both of you spending time and money in court. If that doesn't work, I would suggest that you contact a real estate attorney.

Lou - I have never done a land contract transaction so I can't help you, but would encourage you to consult an attorney ASAP. I will keep my eye on this question ... please keep us posted, as I am curious as to the recommended action and result.