65 year old diagnosed w/advanced metastatic prostate cancer with two lesions on ribs. prognosis/life expectancy/treatment?

Sad to hear about your father's problem. As Yogi Berra once said: it is hard to make predictions. Especially about the future. In medicine it is the same. Without knowing and seeing the patient and reviewing history and all imaging studies no physician should make such a prediction. Discus with his care team if he gives you permission to talk with them.

It could be different initial systemic treatment , the choice depends on comorbidities, presence or absence of the symptoms, previous therapy , result of the tumor genetic testing. Performance status is one of the main factor that helps to chose therapy . It could be cabazitaxel, abirateron plus prednisone, or one of the most effective Radium 223. exercise program, diet are important too.