Quick answer, hope it is enough to get you thinking:
“Who lives by the sword... “ Jesus does not say that it is a sin to live by the sword, else none could be soldiers. He is just saying what can be expected as the result of that as a lifelong tactic. Furthermore Peter might think of wielding a mighty claymore and vanquishing all evil, but as a disciple of Jesus, he chose to take up his cross and die for them. How can I kill you, if I want to die for you?!?
“Turn the other cheek...” Jesus says that you can expect from God the Father exactly what you dish out. So if I have wronged you and deserve a slap, my genuine repentance guides me to go beyond mere eye-for-eye restitution. Since God has forgiven me of so much, so much indeed, if you make me go a mile, I’ll go with you for two.
You are so right about contradictions between proverbs, and you earn my respect to be smart to see it. For example, people will say, “Nothing ventured, nothing gained.” Then another day they might say, “ A bird in hand is worth two in the bush “ Do they not see the contradiction? And if the Bible were such a book, with similar truisms some for Sunday, others for Monday, no man could take it seriously. Patient investigation of scripture paradoxes, always reveals deeper truth.
So when Jesus cleanses the Temple is He contradicting Himself? No He is correcting the perversion of God’s truth. The money lenders made His Temple odious, the Pharisees, hypocrites, made His law odious. With His sermon on the mount He does with words to the Pharisees what He does to the money lenders with a whip. Far from a contradiction, it is perfectly consistent. In the Temple He overturns tables, on the mount He overturns teachings.