Hello David,
Thank you for your message.
I'm glad to hear you figured out the port issue.
also, how can I customize the rdp settings, such as screen size, full screen, smart scaling, etc.
To customize the RDP settings please do the following:
1. In the main Viewer window right-click on the Host icon and choose Properties.
2. Go to the tab Connection -> RDP.
3. Click Configure.
4. The native RDP window will open where you can customize the connection settings.

is there a way to use a .rdp file
Unfortunately, the RDP mode in the Remote Utilities doesn't allow to open .rdp files. To customize the connection settings, please follow the steps above.
Hope that helps.