Looking at the change in temperature between the idle and load states (16C) I would advice you to upgrade to a better cooler to allow you to overclock far.
An increase in voltage does significantly increase the core temperature if heat can not be removed by the system cooling fast enough, this will build up if it can not be removed and may in the end cause TM1 to activate.
Your processor, the 630, is built on a core called the Prescott 2M, it is a revision of the original Prescott with a larger cache size (~14% slower however compared to a 5xx series CPU) and a few extra features. Its temperature levels should therefore remain within the Prescott levels.
A maximum of 67.7C is the limitation that I would advice on this processor