Yes, MILDIV is what happens to you after Captain's Mast. Basically, they are back in boot camp for up to 45 days. Instead of the lovely 2 to a room, 4 to a bathroom, fully furnished dorm rooms we have at A-school, they have 4 to a room, many to a bathroom, minimally furnished rooms. They muster in the morning for a daily uniform inspection, march to breakfast together (shouting the Navy Ethos, 11 General Orders, Sailors Creed, etc. instead of cadence), march back to do some landscaping, march to lunch, march back, more work, march to dinner, march back and do more work. Sometimes they carry sanbags back and forth, from one pallet to another, by the Bowman Center. They have to wear bright yellow safety vests at ALL TIMES so everyone knows that they are in trouble. They are not authorized civilian clothes, and are only allowed phone calls at certain times during the week in the BEQ phone room. Why do I know so much about them? My current BEQ room is around the corner from theirs and see them muster every morning on my way to class. I'm sure that they have to do more that I'm just not aware of, but that's my understanding of what their life is like.
On the other topic here... definitely follow the advice of withroaj. We only have one married guy in our class and his wife was having issues with the changes. She started making friends with neighbors, and other shipmate's wives. It's made her life much better while he's having to spend 15 hours a day with us in the classroom. I can't imagine that it's any easier due to the MILDIV situation. Good luck to you and your husband. He'll be done and back into classes in no time. He'll also probably be a better sailor than most after it's all over.
