4.3 Ghz should be fine.
4.4 and up is stretching it a bit unless you have a really good case with good airflow.
1.2 volts is way too much for idle !
Normally almost all 3570k should overclock to 4.2 without touching voltage, for 4.3 you might need a very small boost (0.02-0.04) for stability.
And about temperature, anything under 70 is ok for long term, considering that tJMax is 105 ..., even 80 should be ok but nobody knows right now how a CPU heated to 80+ would behave in 2-3 years time.