How accurate is Ilm-e-Jaffar in predicting one's life events such as their spouse, number of children they'll have, age and time of death?

The real Ilm al-Jafr was with the Imams of Ahlulbayt (a). They had access to it, and some of the close companions had some access to it.

The Jafr that some people claim have today is unfounded, and there is no evidence that it’s legitimate. So I don’t think it’s accurate in those predictions.