How can I configure the system so that after the Host is re-booted it will re-connect to the Viewer?
I'm afraid there is a contradiction. You mentioned that you needed unattended support and yet you set the Host service to start manually. With that setting on the Host won't start after the reboot unless someone on the remote side starts it (Windows Start menu -> Start Remote Utilities Host).
Perhaps, what you are really looking for is the Ask User Permission option. When this option is enabled the remote user's explicit consent is required to actually start a remote session even if the Host service starts automatically with Windows (which is the default option).
In the Viewer interface you can set scaling (see options on the toolbar - Normal, Stretch etc.) that is you can shrink the remote image to fit the bounds of your Viewer monitor. However, if you want to change the very resolution of the remote screen you will have to do that on the remote desktop itself, that is by accessing the Windows "Display settings" menu.
In the future though we might add an option to change the remote screen resolution from within the Viewer.
There is yet another thing if you want a clean re-install. Please, close the Viewer and erase the entire folder \%appdata%\Roaming\Remote Utilities Files\ then start the Viewer again.
Warning: your address book file/files are in that folder, specifically the general address book (connections_4.xml) and maybe other books that you created. I recommend that you copy these books elsewhere for importing later after you've finished.
but every new MSI i've configured is giving me this same error when i try to add by code.
I recommend that you add the Viewer's %APPDATA% folder to your antivirus software exceptions first. Perhaps the keys.dat file is getting corrupted or deleted by a/v software each time it is created by Remote Utilities.