I've been reading around a few places, and some places say that lowering the multi and raising the FSB will actually decrease real world performance, and I was wondering if there is any truth to this. I want the most out of memory and my CPU.
No, it's actually the complete opposite. Higher FSB = more bandwidth between the CPU and RAM meaning you can run the RAM at faster speeds.
However, the higher the FSB, the more stress is placed on the north bridge meaning that you will often have to settle for a lower FSB and a higher multiplier to achieve stability rather than a lower multiplier and a higher FSB.
Ex: 500x8=4000MHz 400x10=4000MHz. A 500MHz FSB speed places a lot more strain on the north bridge and may not be stable compared to a 400MHz FSB. TBH, the performance difference between 400x10 and 500x8 is going to negligible. I recommend you use the 9.5x multi available to you.
And your temps are good. The E8500's max temp is 72c, so anything under that at full load is safe.
To add to ATF's comment about the voltages and degradation, I recommend you pay the most attention to the FSB or VVT voltage as this seems to be having the most affect on the 45nm C2D's lifespan. Do not exceed 1.2V.