I am having a REAL challenge getting the husband of a 88yr. old alzheimers woman to listen.

I am a caregeiver for a 88 yr. old woman who lives at home with her 87 yr. old husband. I have care 7 days a week for 12 hrs/day. Certain routines must be followed in order to keep her hydrated. She recently was hispitalized for dehydration and malnutrition. This was unfortunately the wake-up call for the family and I had hoped the husband. The challange is he will not "hear" that he needs to allow her to drink after 6pm. regardless of her needing to get up during the night. She has PM meds that should be given around 7pm. not before due to the sleepiness she gets. Medical professionals and myself have explained all the reasons why. Did not work. I truley fear he is creating a bad situation. I have run out of ideas. HELP.