Bethesda add-ons tend to break games on PS3 because they are inept at coding for them. This is nothing new.
See what happened when 4J did a proper port for Oblivion, with optimization, then what happened when Bethesda ported the DLC's to them as it had several major bugs and were never fixed.
Honestly, the information was out there for you to read for a looooooong time that FONV is a terrible game on the PS3 when you start throwing in add-ons, and the GOTY edition is better off being a coaster, so that's on you for not figuring out stuff before you bought it. Doesn't excuse Bethesda from making a shoddy product, but you should have known better as a consumer. Return it within the 30 days or whatever to get a full refund.