Anything you put in the pot should be rinsed as soon as it comes out; cleaning up dried pea soup is not fun.
The soup burned! Its ok take a deep breath! If it has just stuck on the bottom of the pot and burned lightly, you will be fine. Don’t loosen anymore of the burned soup from the bottom, it could affect the flavor. Remove the pot from the stove and pour soup into another pot, don't scrape the burned bottom, put new pot on the stove and finish cooking. No one will ever know.
This is a great soup to serve after it has been refrigerated or frozen, so don't worry about the large quantity of soup you are making.