Am I legally obligated to be my Dad's caregiver?

I am an only child. My mother passed 14 years ago. I've been estranged from my abusive father most of those 14 years. 4 months ago he accepted an invitation from me to go to dinner for his 80th birthday. We had not seen each other in about 8 years. Since then I have been drawn into his mess of a life, including his giving tens of thousands of dollars to a 25 yr old male drug addict who stole my father's check and committed fraud against him. The bank told him they would not longer allow him to have a checking account that was repeatedly vulnerable to fraud. The police are trying to get me to take my dad to a doctor to have him deemed "lacking capacity to give consent" so they can bring charges against the drug addict. My father alternately begs me for help with his finances, etc. and tells me to get the hell out of his life. I've spoken to him with respect, have refused to rehash the past with him and have been honest in all I have done to help him not to be vulnerable to fraud again. I am about ready to walk away from him for good. What are my legal responsibilities to him at this point?