For the LDT, there is a decent chance that your board auto lowers it when increasing the FSB, but you should check for sure and lower it if necessary.
Like has been said, you want to keep total HT at near 1000 or below. That calculation simply consists of LDT multi X HTT (FSB).
So at stock:
200x5 = 1000
As soon as you increase FSB above 200, you should lower LDT to x4, x4 is good to 250 FSB shown below:
250x4=1000
Now, as soon as you increase FSB above 250, LDT should be lowered to x3 and is then good till FSB hits 333. Understand?
I would guess that your CPU is just maxing out at that vcore, but you have quite a bit of room on vcore right now. You will be completely safe up to 1.6 as long as temps stay in check, so keep an eye on them.