Renting from father-in-law, unpaid rent?

I am still married and our marital residence is technically a rental property owned by my father-in-law. There is a lease that only I signed which was effective from around February 2010 when we first moved in (do not have a copy). The lease if I recall correctly was for $3000 a month. Which amounts to approximately $180,000. I only have proof of payment to my father-in-law of $27,550, and I have not made any payment to him since May 1,2013 and I have never paid him the full $3000 in a month.

My wife always threatens that he will sue me for the back rent if we ever divorce. The rental agreement was originally signed to show rental income for the property when he was qualifying for the loan to buy the property, and technically (gentleman’s agreement) there was never any intention for me to have to pay the entire $3000.

Can he sue me for back rent and if so, how far back can he go? He has never sent me any notices of stating that I was past due on the rent or served me with eviction notices.

This question is not related to divorce or divorce related issues, and thus is outside of the scope of this forum.