I have used Immodium in a crunch when I had an event that was must-be-OK type and it sounds like your dad is in a very bad flare. Sleep is important for both the brain and the gut. But as a permanent addition Immodium is not good because it will hurt the gut's natural rythym in the long run. But for a short while it won't cause any permanent harm and can be very helpful to stop a dangerous cycle of D which can deplete his body of fluids and nutrients.
My sig. tells you what helped me.
Best wishes to you both. I remember when I was finally able to sleep through the night. It was bliss that people without UC cannot imagine.
In remission April 2010 after 10 years of suffering and no remission ever
Jan 2010 started SCD diet (modified to remove dairy, fruit & juices)
Bleeding stopped in 3 days, 95% remission in 5.5 months
Diet: Gluten/grain-free, fructose-free (blueberries OK), dairy free (swiss cheese OK), starch-free
I eat: Protein(meat/fish/eggs,no soy), nuts(soaked/roasted), non-starch veggies, nut-flour muffins
Daily: fish oil, Vit D3 2000 2Xday with oil/fat, veggie juice, sunflower seeds, probiotic VSL#3
homemade yogurt and some fruit OK at 5.5 month remission
Highly recommend: the book "Life without Bread" and the Specific Carbohydrate Diet