Sounds to me like it might have something to do with your gpu. I would suggest removing the OC on the gpu for the moment and see if SH4 will play normally with the gpu at normal setting.
One other thing I see and that is where you have the game installed. Now some people say it doesn't matter and others say it does. But try re-installing the game to another place on your c:drive other than C:\Program Files (x86). See if things improve.
One other thing and I'm not sure about this one. You have the environmental mod installed before RSRDC. I believe that RSRDC should be installed first before the environmental mod, but here I'm just guessing.
I hope you solve your problem and someone has the correct answer for you.
