How to generate a report showing all, or selected resources across all or specific projects.

You would need to use the R_ProjectReleaseResources entity, and/or you can join other tables/entities to that using SQL Joins to get additional columns. Without knowing exactly what you're looking to achieve, I cannot give the exact SQL. If you can list out the columns you need I can see what might be possible. Also in terms of the other questions, there is not a way to add additional customized options to the progress drop-down, and that dropdown is not currently multi-selectable.