You might lose your events if you cut your computer's power while Rainlendar is updating its events file. It's not likely to happen though since the events file is written only when you add or edit the data on it.
The automatic backups are fixed to be done daily but you could create a script which runs the backups more frequently. It might be easier though to use some 3rd partly backup tool to make a copy of the Rainlendar's data folder
The 'unusual' lines in the log just mean that you don't have the Gnome keyring installed so the passwords cannot be stored to it. In this case Rainlendar will use its custom password encryption method.