Can't find a few verses, please help.

I may be able to help you with the first one. I believe the verse you are talking about is Matthew 18:6

But whoever causes one of these little ones who believe in Me to sin, it would be better for him if a millstone were hung around his neck, and he were drowned in the depths of the sea.

Hope that helps.

I'm a little new at this, but here are a couple possibilities for the second one.  Matthew 5 starting at verse 17

Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill.

Also Luke 16:16

The law and the prophets were until John. Since that time the kingdom of God has been preached, and everyone is pressing into it.

My concordance is showing the word "anger" being used 19 times between 1 and 2 Kings.

This is a 1 in 19 chance, but what about 1 Kings 14:9?

"but you have done more evil than all who were before you, for you have gone and made for yourself other gods and molded images to provoke Me to anger, and have cast Me behind your back--

On the second point.
I do not think that Jesus ever said exactly why, he simply stated that "I am the way, the truth, and the life. No one can come to the father except through me" John14:6.
Paul, however, gives a clear exposition in Romans 3:21-31. In essence, the law told mankind how to live as children of God, but as everyone falls short of it we needed Jesus to save us from the punnishment we deserve for breaking the law. So "The law no longer holds you in its power" Rom 7:4.
See also Psalm 14:3 - no one is good. Job 9:33-35 - If Job, "a man of complete integrity" 1:1, needed a mediator, how much more do we?
Luke 13:1-5 - Jesus makes point that everyone is a sinner who needs repentance.

Hope these are some help.