1. If you only overclock slightly, you won't see any real difference. Really I can't comment on that, though, because I don't know how you are determining the difference or the rest of your system setup. If you're just basing it on how the game "feels," then it's because most people couldn't tell anything under a 5% difference (in general), and this is even harder to see in games. Also, depending on your resolution, AA/AF, and in-game graphics options, you might still be bottlenecked by your video card. Even if that's not the problem, there can be any other number of reasons that a CPU overclock did not translate into significant gains.
2. Although I don't want to put words in Jerm's mouth, timings generally refer to CAS-tRP-tRCD-tRAS timings (e.g. 2-3-3-7).
3. Timings are different than "speed" in that speed dictates how fast the RAM talks to the CPU, and timings dictate how fast the RAM can get the data from within itself. Decreasing timings and increasing "speed" should both increase overall performance.
4. Why is Forgotten Hope uber RAM intensive?
5. For the original question, yes it should. More bandwidth means that, assuming your processor is up to it, you won't have as many wasted cycles while your CPU waits around for the necessary data and that your processor is able to get more data sent in the same time frame. Waster cycles = bad, FYI.