When hyper, I took my methamazole and beta blockers before bed. It seemed to help with sleep and I didn't need the afternoon nap.
When I was super hyper, and I often still get insomnia, I used valerian. It comes in a capsule or tablet and it works really well. Natural herb. It is often used as the base for stronger insomnia medications. It works really fast. I used it for my daughter after a major life threatening operation as she could not sleep. Zonked her out for hours!
Morphine is a pain relief and should only be used as such. It is highly addictive and your grandfather may have been using if for more than just insomnia. No doctor would prescribe it just for insomnia.
Here is a link of possible interactions. don't believe it would interact with your Methimazole.
http://www.umm.edu/altmed/articles/valerian-000934.htm
Try warm milk too!
Morphine would be the last resort as it can upset every organ in your body.
And if your Father was on Morphine, he wouldve had a medical condition a lot more serious than Insomnia.
Whe was your levels checked last and what were they?