That's exactly the same model I have. If it's not too much trouble can you post your picture settings for gaming? You're probably using the Game mode right? Did you make any changes from the standard config?
Everything is written in french so I'll just post what my settings are just bare in mind that the luminosity will be too low but my girlfriend is photosensitive, so adjust the brightness as you want.
I'll try to translate as best as I can but if you have some doubts i'll go over them sequentially, hoping is it the same in every language.
my settings are for the game mode:
luminosity 5
contrast 90
gamma0
black level 50
black settings no
enhanced contrast non
local dimin low
extended dynamix range no
color 55
shade 0
color temp expert 1
natural color no
sharpness 50
reality creation no
random noise reduction no
digital noise reduction no
motion flow no
movie mode no
hdr mode auto
and all the rest was predefined.
I think what should work best for you is to try to tweak with motionflow since it interpolate frame it can give a feeling of stutters.
If all of that still makes it painful to play 30 fps games maybe check for update or reset it.
That being said my pc is plugged to this TV too and I can feel much more the difference between 30 and 60, since the screen refreshes at the rate of the video I can always tell when I'm watching a 30 fps video on how my mouse looks.It may be due to the moving pixels resolution i'm not sure how it is called in english.