hmm.. I'm not sure that they understand what you're trying to do. And I certainly don't think that downgrading it is the correct solution
One thing to note is this: Cheap shared hosting accounts do not normally include additonal distinct websites. They may say that they let you host unlimited domains, but those must all be the same website. For DNN to give you multiple sites with different domains you need to be able to add another website to your hosting account. This is different from adding another domain alias to the account. Additional websites can have their own email services. Additional domain aliases cannot.
Tell your host that you want to add another website to your account. There is usually a small fee for this.
Once the new website is added, there should be an option in your hosting panel to point the new website to a folder - point it to your DNN root folder.
Rob