# He did what was right in the eyes of Yahweh

"He did what Yahweh considered to be right" or "He did what was right according to Yahweh" 

# He walked in all the way of David his ancestor

"He lived the way David his ancestor had lived" or "He followed the example of David his ancestor" 

# he did not turn away either to the right or to the left

"he did not do anything that would displease Yahweh" or "he fully obeyed all the laws of Yahweh"