Yes, by using the baseurl: https://download1.rpmfusion.org
But it is probably slower than doing it manually if you do only need a small number of repositories.
Yes, but there are some limitations like you can not use it as synced content during provisioning, no errata support yet, …
There is one more thing about templates. We have a new page you can find under Administer > About > DSL Templates. It’s documentation similar to API docs, but regarding macros available to use within a template. There is also updated Help tab on that page.