Hey Neogaia! How's life?
About your question regarding 1st John, I'd look to John himself in context to answer the apparent "contradictions." And in the case I believe you are referring to (1 John 2:1, compared with 1 John 3:1-10), the answer is that John was using the analogy of
adopted children of God (1 John 3:10). As such, John is never talking about sinless perfection in the letter, but about sons who enter into obedience, respect the Father's commands, and do everything in their power to fulfill His wishes. The sinners in this context are those who refuse to honor the Father's Lordship over their lives, and so give themselves over to sinful behavior by willfully
rebelling against His wishes.
But as for Jesus' words trumping those of the apostles, you can
best believe they do brother.
This might get into the issue of infallibility again, and I've been accused of being a "false prophet" once too many times already this week. But yes, His words and His teachings bear more authority, and always will.
God bless you, Bro!