We had a similar issue. I live in NJ. Our home is 30 years old. We had lots of cracks around our staircase area and entrance to our living room. Prior to painting the entire inside of our home, my husband and I carefully gouged out the cracks and uneven surfaces. We used spackle for the small cracks, and auto Bondo for larger cracks and uneven areas, then sanded and primed the areas, prior to painting. We spent hours doing this. We learned about Bondo, when we had our kitchen and 3 bathrooms renovated a few years ago. Our experieced carpenter recommended we use auto Bondo to repair large cracks and uneven surfaces. My husband was quite familiar with Bondo, as he restored lots of autos. Well years later, all our restored areas still look great! I mentioned the Bondo, for anyone fixing large cracks.