Yeah im not too sure whats going on with your mem, i just leave pagefile on auto, its set to 5gig atm. I would start a thread about that on the mem forum page.
For settings with that card ya should be able to run everything on max except Grass on Vhigh not ultra. On advanced graphics you can turn on Long shadows and detailed streaming but leave off High res shadows, frame pacing and only use a few ticks of Extended Scale Distance at most.
My i7 might be giving me a boost over your i5 so yours might not yield exactly the same results but i got a solid 60 fps with them settings. Thats using vsync and a 60hz monitor. If it is the case my CPU is boosting my low end FPS preventing stutter, it might just be a case of dropping a few settings, i would start with grass and particles as theyre very demanding and dropping them both to high cane give you a big boost.
Some people would prefer to turn down some settings to gain more AA or increase the extended scaling distance but thats all down to personal preference.
I get crossfire stutter so i need to limit the frames to 59 to eliminate it but using a single card you shouldnt get this as i didnt when i disabled crossfire, maybe your not using a 60hz monitor and vsync the same as me?