The Question and Answer section for The Old Man and the Sea is a great resource to ask questions, find answers, and discuss the novel.
I think fighting the great Marlin for so long was the biggest decision Santiago made. It came down to the death of the marlin or the death of him. Santiago was willing to give his life to the majestic fish that he was fighting.
Santiago and the boy are close friends and partners. The boy loves Santiago.... he is his mentor and friend. Manolin calls Santiago old man lovingly.... he's not demeaning him or being disrespectful, it's just his way of speaking.
Santiago beat the marlin with patience and skill. Santiago was beaten by the sharks that attacked the marlin, tearing it to bits before he could return to shore.