Tums is just used for the calcium. Powdered milk is just used for the calcium. Epsom salt is magnesium. Calcium from any source would work. I use Dolomitic Lime. That takes care of the Ca and Mg. You'll still have some blossom end rot, regardless of what you do. Tomatoes that set during cool weather or cool nights, are gonna have it. The first few tomatoes off each plant usually have it, regardless of what I do.

If my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land. 2 Chronicles 7:14