Question 1:
According to his speech, this "good society" will be able to defend itself against schemes of world domination and foreign revolution.
It states clearly in the speech, "A good society is able to face schemes of world domination and foreign revolutions alike without fear."
Question 2:
In this passage, "you" refers to Congress.
Imagine the sentence like this, "If the Congress maintains these principles...will give you their applause."
"You" is referring to the Congress and their is referring to the voters.