Try QPI on 1.3V-1.35 for 3.8ghz, it doesn't have to be the same as CPU volts no, just make sure that QPI voltage and DRAM voltage are within 0.5V of one another (so with a 1.3V QPI keep DRAM volts below 1.8V).
HT = Hyperthreading, it basically gives your CPU 4 more threads and uses areas of the CPU that would be otherwise idle, obviously the more of the CPU that is being used at the same time the more heat is generated.
EDIT: If you download "TurboV" from the Asus website you'll be able to see what volts your QPI & DRAM are being set to as they aren't shown anywhere in the BIOS, I remember when I left those voltages on auto they got set really high when overclocking.