God's servant will be gentle and kind. Both "bruised reed" and "smoking flax" represent weak and hurting people. Alternate translation: "He will be kind to people who are like a bruised reed, and he will be gentle to those who are like a smoking flax"
"he will not put out any smoking wick" or "he will not stop any smoking lamp wick from burning." A smoking flax is a lamp wick after the flame has gone out and when it is only smoking.
Leading someone to victory represents causing him to be victorious. Causing justice to be victorious represents making things right that had been wrong. Alternate translation: "until he makes justice have victory" or "until he makes everything right"