However, the man is dying.

• Assuming OP's dad is between 40 and 64 his life expectancy is only about 10 years shorter than the general population. Source below. So no he's not dying.

.... give him that

• Who are you to instruct OP to give this man anything?

Also consider this: when he passes away, will you have no regrets about how you handled the situation?

• 100% agree this is the $1,000,000 question here.

"The mean life expectancy of patients with PD (Parkinson's Disease) compared with the general population were:

38 (SD 5) years for onset between 25 and 39 years compared with 49 (SD 5) years;
21 (SD 5) years for onset between 40 and 64 years compared with 31 (SD 7) years;
and 5 (SD 4) years for onset age ⩾65 years compared with 9 (SD 5) years."

https://www.ncbi.nlm.nih.gov/pubmed/17400591