Check your card temps with systool or the nvidia control panel you can use speedfan too but its slightly off with the reading. If you add a modifier to the reading in the speedfan properties based on the control panel temperatures and leave speefan running when you play it a game it will record the highest and lowest temperatures that the card makes.
As long as your card isnt getting to hot you can disable Nvidia Throttling which is probably whats causing your screen freezes.
Download a program called RivaTunar from
HERE Go to Power User then into Nvidia \ Overclocking go to a option called EnablePerfLevelForcing and set to 1. Then save it and i think you need to restart. This should stop throttling.
Yes disabling sideband might help but its not worth it because the performance loss is to great. Also i would turn vagp voltage back to 1.5 and bus speed back to 66 for now. disable Fast writes though as that doesnt effect performance and does help.
If its only battlefront 2 causing problems you might want to try a different set of drivers also.