I would recommend seeing an attorney. Your father's money is to take care of him. You may need a conservator... It makes it more difficult if they have transferred assets and it causes issues in MediCal eligibility... See an attorney quickly
This is not intended as specific leal advice and is based in California law
You need to apply for conservatorship (conservatorships in California are used for incapacitated adults while guardianship is used for minors) if you wish to make decisions for your father. You may also wish to contact Adult Protective Services (APS) if your father was financial abused.
No legal representation exists by virtue of this answer. It is recommended that you contact an attorney directly for a more complete response.