Like the title says, this is not a permanent fix to the lag issue, all I want to know is if anyone knows how to reduce the amount of lag, so far, I only know of turning off the auto save feature. Is there anything on the PS3 system itself that I can enable/disable so that not much RAM is used? Thus, providing about an extra 2-3 hours of playtime.

simply saving and restarting your ps3 can fix the issue, atleast for afew hours. also deleting the game data(not your save data) and reinstalling might help.
disconnect your ps3 from the internet and disable notifications too.