1- Maybe isn't safe with that RAM, since isn't a very good manufacturer u can get some BSoD with the OC.
2- U can reduce the ratio of the RAM, with that when u OC the CPU, the RAM will be running at 400MHz, that is stock for the RAM.
3- If u can buy a better RAM could be a good option BUT bear in mind too that the price of DDR2 is very similar to DDR3.
Well it's doable. However you can usually adjust the RAM ratio to the FSB, so if you choose a FSB that will multiply properly to get the stock ram speed, that would be best. For example, I had my FSB OCed to 160 so the RAM was at 10x for 1600mhz (DDR3). I now OCed the FSB up to 200, so the RAM is at 8x. With a higher FSB you might have to increase VTT voltage, and also adjust the CPU ratio to keep it at the OC you want (for example I use x18 for 3.6ghz but I could use up to x20 for 4ghz). Of course being able to do all this does depend on your mobo and BIOS options.
Anyway, from what I understand it should be safe to do it so long as it's still stable. If it's unstable, you'll need to increase RAM voltage a bit which can start to be unsafe if the RAM isn't capable of handling it. If necessary, you'd be safer to underclock it and try lowering the timings as much as possible to get somewhat similar performance.
OMG, NO, don't do it. Value ram is like nitro when it's OCed, it could take out your whole house.
Now on the serious side, as long as you don't go nuts with the voltage the only thing that could happen is your computer will become unstable. So, if your within the voltage specs and it's stable, no worries.