Yes, you may have to loosen the timings as you increase your memory speed, but probably not until you're above 850 mHz. Yes 1T is faster than 2T. But hold off on memory OC until you're done with your CPU.
CPU Voltage - Yes, there is a max voltage on the box. This is max for stock operating speeds. However, I don't think it's max rated for the CPU (I believe it is 1.35V on the E8400, can be found on Intel's site). Once you go over the max rated, no more warranty from Intel. You will have to increase voltage as you raise the FSB.
If your system boots and is stable (no BSOD, no reboots, runs Prime95 or Orthos without failing), there's no reason to raise vCore unless you want to try raising your FSB.
Don't forget to come up for air every once in a while, take your wife to a movie or whatever. I just tell mine I like doing this as much as she likes scrapbooking.
