So sorry to hear about your dad's condition. It must feel quite helpless for you and your family to be unable to do anything for him from so far.
Sorry to know you were refused. However, it was expected for the reasons I had stated in my first post on this thread. Visa officers are human just like the rest of us. They have the challenging task of deciding who should be granted TRVs. Humanitarian reasons are considered while granting visas. But, unfortunately in your case, your stay could get extended even indefinitely due to your dad's health conditions. This indeterminate stay is untypical of a visitor.
On the positive side:
It is good that your dad's tumor is not spreading. Hopefully he will get stronger and he will recover fully when he is with you and your family.
Don't let the TRV refusal to affect you. Don't lose hope