1:5 and from Jesus Christ, the faithful witness, the first-born of the dead, and the ruler of the kings of the earth. To Him who loves us, and released us from our sins by His blood,

and from Jesus Christ

The continuation of the trinity from the previous verse.

1) the faithful witness

Past - His earthly life of obedience as given in the gospels.
Present - His witness to the condition of the churches both in chapters 2 and 3 and present day.
Future - His finality when all things are consummated under His control.

The world doesn't like His witness (John 7:7) because its the truth (John 18:37) in spite of religious or political leaders who crucified Him (1 Timothy 6:13).

2) the firstborn of the DEAD and

Jesus Christ was the first one to be raised from death...those of us who believe this have the same opportunity of resurrection - Revelation 7:13-14.

This verse is the only place John uses this expression, "firstborn". Paul was fond of it. He used it in Romans 8:29, Colossians 1:15-18, and Hebrews 1:6. Jesus Christ conquered death in all its forms - creation, human, and even/especially spiritual.

Rabbinic tradition also believes that Psalm 89:27 really refers to the Messiah even though it is written about David.

3) the RULER of the kings of the earth.

This is a key theme of Revelation. It is used in Revelation 11:15, Revelation 17:14, and Revelation 19:16. Who are the kings of the earth?

     -  political leaders (Revelation 6:15, Revelation 17:2)
     -  Satanic leaders/demons (Revelation 1:18)
     -  believers (Revelation 2:26, Revelation 3:21)

John is not clear which of the above he meant. Maybe all of them.

TO HIM who

a) LOVES US (present tense) Romans 8:37-39 and

b) RELEASED US (past tense) Revelation 5:9 and Revelation 7:14 from our SINS by HIS BLOOD,

We, as believers, do/will overcome the devil because of the BLOOD of the Lamb (Revelation 12:11). The devil can NEVER undo that act of SALVATION that Jesus Christ did at Calvary and His subsequent resurrection!!