No, there is no contradiction. The Greek says:
καὶ εἴ τις οὐχ εὑρέθη ἐν τῇ βίβλῳ τῆς ζωῆς γεγραμμένος, ἐβλήθη εἰς τὴν λίμνην τοῦ πυρός
And if a certain one not was found in the book of the life having been written he was cast into the lake of the fire
First, John doesn't even say it's necessary that anybody be thrown into the lake of fire.
Then (with a modified KJV):
ἔξω οἱ κύνες καὶ οἱ φάρμακοι καὶ οἱ πόρνοι καὶ οἱ φονεῖς καὶ οἱ εἰδωλολάτραι καὶ πᾶς φιλῶν καὶ ποιῶν ψεῦδος
"[For] without [are] the dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie." Revelation 22:15
So I don't understand this as saying the "dogs" and such "are outside", but that those within the gate are without such wickedness.
As Witness said, everything in Revelation was "signified", so your guess is as good as mine. As far as comparing it to the parables in Matthew 8:12, 22:13 and 25:30, I think it's better to compare it to passages when Yeshua was being very literal:
"Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy.
But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;
That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust.
For if ye love them which love you, what reward have ye? do not even the publicans the same?
And if ye salute your brethren only, what do ye more than others? do not even the publicans so?
Be ye therefore perfect, even as your Father which is in heaven is perfect." Matthew 5:43
Is loving our enemies crucial for becoming perfect? Yes.
Does God possess this perfection? Yes.
Is burning our enemies in an eternal torture chamber forever and ever (whatever that means) an act of love? No, not in any circumstance whatsoever.