I would not be unduly worried about your relationship with the landlord and what he might say. If your lender contacts him it will most certainly, and probably exclusively, be to obtain a verification of rent (VOR). So long as you've made your rent payments on time, I cannot see how anything else he might say would enter into your new loan's qualification.
If your loan application and previous residence history is accurate, and you've always paid rent on time and this can be documented, you should be fine.
Keep the faith and good luck in the new home!