there are the “(no board)” and “(no sprint)” members in the Sprint dimension showing issues not assigned to any sprint currently.
For the average resolution time, please use the standard eazyBI measure “Average resolution days” in the Calculated members of the Measures panel.
You can combine the measures with the statuses in tuples to see the readiness of the backlog. Use the formula like this:
([Measures].[Issues created],
[Status].[Ready for Dev])