These lines come from American poetry in the 19th century. This is an epic poem called "The Columbiad" made by Joel Barlow in 1807. The author wants to show how U.S. citizens imagine their national identity by stating good principles for a good nation. In his ideas, he attempts at social, cultural and political emancipation. In the first lines "Purge all privations from your liberal code, restore their souls to men, give earth repose, And save you sons from slavery, wars, and woes" the author's argument is to seek for life, liberty and the pursuit of happiness. In order to achieve that he believes that slavery should be abolished so the United States will be purge of the crime of slavery. He believes in freedom, in a new country with good foundations for liberty and progress.
In the next lines "Based on its rock of Right your empire lies; On walls of wisdom let the fabric rise; Preserve your principles, their force unfold. Let nations prove them and let kings behold." the author argument is the same, he is constantly searching for liberty in his ideas, he thinks that the United States should end slavery by eliminating slavers and masters. This idea is important specially because the author believes in a republic society that can't failed. He constantly says that slavery is barbaric and it doesn't fit in a democratic new world. For a good nation it's necessary to have good principles, wisdom and liberty as well as good citizens with a new mind that means without the european tradition and slavery.
3. to flow out is to spill forth
True, you should always be familiar with the text.
