hi your pc should be enough, you could try uninstalled video card then installing it again and it should give you the right update for your card,
also i have a nvida gt710 2gb card ,resolution has always been 1024x768x32 ,
and i run FPS unlimted , mine is the disc version of fsx with acc packand with lots of mixed add ons via download and discs,
tbh when i tried setting my resolution ages ago it would not work or look all strange
only dlc i had problems installing disc version was space shuttle , but thats now been fixed,
i would make sure in the future that you delete all files related to fsx, ,that was my origanal problem and somewhere i had a dupi set of FSX files messing with each fresh install of FSX
but default resolution for mine has always been ( 1024x768x32 ) and it runs pretty much perfect ,
cheers mark