Unfortunately, that's the reality, you can stress test for hours but you may still get unexpected crashes/freezes/BSODs during every day use – until you get a stable setting/voltage.
But, you're doing the right thing - incremental voltage increases, until it proves itself stable (stress testing and everyday usage.) - and hopefully, lower temps.
But, you're doing the right thing - incremental voltage increases, until it proves itself stable (stress testing and everyday usage.) - and hopefully, lower temps.

thinking of maybe buying a E5300 or something to replace this not got the money to get a new system unfortunatly