When you say set the RAM to half, you mean actually lower it from 800MHz to perhaps a lower speed?
You overclock your processor by increasing the FSB frequency. It starts out at 1066mhz at factory settings before you overclock.
While increasing your FSB, keep your RAM speed at exactly half of what your FSB is. Say, for instance, you increased your FSB to 1400. Set your RAM at 700mhz.
It won't hurt your RAM to downclock it a little. If you want, you can mess around with the timings and see if you can get the timings lower since it's running at a slower speed. Often times, memory that is underclocked will be able to hit better timings than at its stock speed.
And the voltage on your components is increasing because you have it set to "auto." If you want that to stop, you need to set the voltage manually.
The 6600's will get up to around 60C under dual-prime stress-testing when you're on air cooling and pushing more voltage. That's normal. To remedy the issue, go with a good aftermarket heat-sink fan like a Tuniq Tower, Arctic Freezer, Scythe Ninja, etc. The stock Intel HSF's are very weak and make the chip run hotter.