In our climate an insulated outbuilding with no supplemental heat is adequate. Apply Sevin, or Orthene. Repeat sprays as necessary. The traps have not been proven to reduce damage. Blossom end rot shows a lack of calcium in the fruit.
Calcium is a nutrient.
The reason that it isn't in the tomato is because it isn't in the soil. Lime adds calcium to the soil but it takes about 6 months. Lime for next year. Blossom end rot can also occur if the calcium doesn't have a steady source of water to carry the calcium up to the tomato. Regular watering helps more calcium get up to the plant.