He ruled Valencia from 1094 until his death in 1099. It is all but impossible to describe a classic like El Cid with the sort of questions asked above. It is, in fact, literature a thousand years old, and arguably one of the great medieval epics.
El Cid chose not to fight because he was hoping that both armies would weaken themselves. El Cid was a formidable military leader who won several famous battles. He was also an astute politician.