Hi there im not familiar with your bios but where you set the ram timings which you state are 2.5,4,4,8 set these to AUTO and the 400mhz set it to the lowest possible, its either 100 or 200mhz.
As for multipliers the proper way to do this is to increase the FSB and lower the multiplier. But since your new to this i would recommend initially upping the Multiplier by 1 and running prime95 for 5 minutes to make sure all is stable and rinse and repeat. Though you should easilly hit 10. Is 10 your highest multiplier? if so try lowering your multiplier by either .5 or 1 and increase the FSB by 5-10 (Dont make any major jumps 5-10 is about average) If your system starts to restart lower the multiplier a bit more leaving the FSB the same till you get a stable running machine.
After a certain OC you will have to start increasing the voltage of your CPU. Only slight increases are required till you get stability. By slight i mean something as low as 0.025 could be all thats needed of course that is if you have the option for this.
I think that should be enough for now, i dont wanna over load you with too much.
Try what i said keeping a keen eye on temps. Good LUck with the OC and most importantly have fun
NB: Have you found out your motherboards limits as of yet?