Why does my Wordpress site have 404 errors or appear to have broken css if I am accessing it via the IP address and username like this?
Wordpress uses URL/domain name references in the database in order to function properly. This means that you need to have the proper URL of your Wordpress site typed into the address bar in order to see the domain correctly. You will want to set up your local hosts file in order to test your Wordpress site before the DNS is pointed.
You can find information on how to set up a hosts file in the following article.