Why did you enable PLL OV? Turn it off. You don't need it for such a mild overclock, and it may decrease the lifetime of the CPU. You should be able to leave everything on its default setting and change only the multiplier, going straight to 4.0.
That's a little high, yes. Looks to me like you're using the stock Intel cooler, which is awful. You should get something like a $35 Hyper 212 EVO, or a $20 Hyper TX3 if you really don't want to spend money.
What are your other specs?
Most OCing guides are designed to help you achieve the maximum possible overclock, not to do a modest increase.
I don't think OCing without messing with other things, like voltage, will have a significant effect on your CPU's lifetime. Still, a 2500K at 4.0ghz should have no problem handling that card in any game but Skyrim (maybe bump to 4.3ghz there).
If your ambient temps aren't crazy and your case isn't stuffed into a box, you shouldn't really be seeing temps like that. Test again with PLL OV off. How did your TC application compare to this technique? http://benchmarkreviews.com/index.php?option=com_conten...
65C is totally safe, but I'd expect more like 58C.