It wasn’t the news fans wanted to hear. On Feb. 16, Demi Moore gave a heartbreaking update on Bruce Willis’ health battle. “[His] condition has progressed, and we now have a more specific diagnosis: frontotemporal dementia,” announced the devastated actress, 60, calling it a “cruel” disease for which there is no cure. “Unfortunately, challenges with communication are just one symptom of the disease Bruce faces.” Before his health began to deteriorate, though, Demi made her ex-husband, 67, a promise. “She told him that she would always care for their blended family,” reveals a source. The former couple, who share daughters Rumer, 34, Scout, 31, and Tallulah, 29, divorced in 2000 but have remained close, celebrating the holidays together with Bruce’s wife Emma, 44, and their girls, Mabel, 10, and Evelyn,…