# You have shown great covenant faithfulness to your servant

"You have been very faithful to your covenant with your servant" or "You have greatly and faithfully loved your servant" 

# because he walked before you in trustworthiness, in righteousness, and in uprightness of heart

"because he was trustworthy and righteous, and his heart was upright" 

# in uprightness of heart

"he was sincere" or "he spoke the truth and did what was good" 

# to sit on his throne

"to rule in his place" 

# today

Solomon is speaking of the years he had already been ruling, not of the time since the sun had last set.