Set PhysX to AUTO, remember that BF3 does not use PhysX
While you have a small CPU bottleneck, you do have the cards needed to play well.
There is no need to use the settings "presets" as that drops all kinds of stuff in the BF3 in-game settings.
All you need to do is get your VRAM pool size down and then drop only the settings that are hardest on your CPU.
Use the "Custom" BF3 in game preset and set Texture Quality to HIGH (that will drop the VRAM)
Then set Motion Blur and HBAO to OFF
Drop EFFECTS to MED
Dont use Deferred AA, set that to OFF and use the PostAA and set that to HIGH
That should help even out the FPS a bit and raise your min FPS