You have a good clinical trial; the same one was helpful for my wife on existing sites. Unfortunately, it did not stop additional new sites spread to her liver.
The side effects are very hard, but the ones you mentioned are normal. If he has lost use of his hands he probably needs to change chemo treatments.
Your oncologist can recommend other chemo treatments; all will have difficult side effects, some more than others.
My prayers are with you; Melanoma is a terrible and merciless disease, my wife and I have been fighting it for nearly seven years, four different chemos, two surgeries, and still we battle; it just keeps getting tougher.
Always keep hope and get a second opinion. Often one oncologist will give up and another one will try to help.
Enjoy each day with your Dad. That is the most important thing for you to do.