I have used the pumpkin pie recipe from my Betty Crocker 1950 edition for almost 60 years and have never had my pie pull away from the crust or crack thru the center. There has never been a recipe, according to the folks that have tasted my pumpkin pie, that can top this recipe. I am inclined to think that perhaps your filling might be too dense and as the pie bakes from the outside inward, it tends to lose too much moisture and therefore pull away from the crust. I always bake my pie so that the center has the VERY SLIGHTEST shake in the center. As it cools it get firm. My daughter used a recipe that calls for evaporated milk. Side by side, the old Betty Crocker recipe get eaten first.