Do you think that is too close?
Yes. Domestic to Int'l requires you going through exit formalities, unless the IPC flights have special handling. I wouldn't like that connection time.
Is SCL large in case terminals are not close?
SCL is a fairly compact airport.
Would LAN be able to check my flight through if my ticket is with another airline?
Probably - they have interline baggage agreements with most.
Also, we will be flying out of SCL on LAN Business, do we have access to the lounge?
Confused. You said you are flying out LAN Business but you have a connecting ticket with another airline. If you are outbound int'l LAN in Business, you can visit the Neruda or Mistral lounges.