The best advice I can give you is to have your father's oncologist request a consultation with a pain management physician.
As far as your specific questions:
1. Radionucleotide treatment is often excellent for boney pain secondary to cancer. You would be best to discuss this with his oncologist and possibly nuclear medicine physician. Pain specialists
do not work with this type of therapy, thus I am not qualified to address your question;
2. I am not familiar with some of the medications your father is on, specifically Novalgin drops and Tilidin Ratiopharm Plus drops ;
3. His stomach trouble may be related to constipation. It is important to have stool softeners/laxatives on a regular basis when taking opioid (narcotic) medications. If your bowels don't move regularly, you can become nauseated, lose your appetite, loose energy and become weaker. Interestingly, constipation is the most common cause of nausea in the USA; and
4. I would recommend you and your father talk with his family doctor, oncologist, and/or his urologist regarding a pain specialist consultation. Most physicians are happy to do so.
Regards, and best wishes for you and your father.