There isn't a way to create ordered or unordered lists the built in editor, you would need to upload an HTML file for that.
As for HTML rendering differently on the two platforms, we don't currently have a guide for best practices, but if you'd like to send us the file/code I'd be happy to take a look. As for creating custom templates, that would have to be through our Pro Services team, who would need to work with you and create those for you.
Also, it looks like you have email support with us, so feel free to reach out through firstname.lastname@example.org or better yet, fill out the form here with your app info so we can better help you: https://support.urbanairship.com/hc/en-us/requests/new.
Urban Airship Technical Support