Thanks for your question on Health Care Magic.
I can understand your concern.
Sorry to say but there is no total cure for his pain.
Bone metastases related pain is very difficult to treat.
You are giving correct medicines for pain relief.
In addition to those drugs, you can give mild sedative drugs to induce sleep because sleep can give pain relief.
You should also start calcium and vitamin d 3 supplements. These will also subside some pain.
You can also try
acupuncture techniques. These techniques are not 100% curative but can give some relief.
So these are the other options besides what you are giving. Discuss them with his doctor and plan accordingly.
Sorry, but there is no medicine to cure his pain fully.
Hope I have solved your query. I will be happy to help you further. Wishing good health to your father in law. Thanks.