1. Remember that you need to cross the pacific ocean on your RTW ticket, otherwise it's not a valid ticket and won't be issued. There could be an option to have transoceanic surface segment if you start from SWP, though (didn't check the rules but I am sure you have..)

2. Why worry about the "tight" connection if it's legal, if you cannot make it LA will protect you and get you a hotel in SCL if needed? For the rest (like possibly missed hotel reservation in GRU) there's a thing called travel insurance. SCL is quite efficient airport and 1hour is more than enough for the transit including a bit of lounge time if your inbound flight is on time.