MacBook Pro 17" Early 2011 running without the AMD GPU
Adding extra memory to the system is not going to improve the graphics, I'm afraid.

The Intel HD3000 has a hardware limitation of approx. 1.7 GB of system RAM it can use for video ram. So even though you add 8 GB of extra system RAM, you're not going to be able to use more of it for video ram.

As far I know it is possible to set the VRamSize to 2048, which would indicate 2 GB - but in reality only ~1.7 GB would actually be used.

If you want to try that, please change the x60 in your command to x80, and the VRAMSize from 1536 to 2048.

I wouldn't expect that to alleviate the problem with zones of glitches however.