I think it will be okay to answer the phone and keep it more of a 'one sided' conversation. He doesn't need to know you lost your job or SSDI. If he asks you about your job you can just say 'same old same old'. You don't need to speak to him like your long lost uncle that's close to you. But if you keep the contact open, and don't disclose to him what you wouldn't want your father to know, you'll have no regrets if anything permanent happens to him.