Brandon,
1. If the table frame is not showing values for features currently displayed in the map this is likely a bug. To determine that is is a table frame issue, check to see that the link to the table frame's data source, layer or standalone table, is not broken and that you view the fields and values in a Table View. If the layer is broken, or you cannot view fields and values in a Table View, then there is either a problem with the data source (might have been moved, renamed...) or an issue with Pro's ability to stay connected to the data source.
Either way, this sounds like an issue that needs to be investigated. Can you contact Esri Support? They are better equipped to handle troubleshooting steps and gather bug data. They can be contacted at https://support.esri.com/en/contact-tech-support.
If you table source is Excel spreadsheets you might be interested in the following links:
https://community.esri.com/thread/226227-having-trouble-importing-excel-tables-into-arcgis-pro
https://community.esri.com/groups/esri-training/blog/2017/05/26/working-with-excel-data-in-arcgis-pr...
Excel To Table—Conversion toolbox | ArcGIS Desktop
Work with Microsoft Excel files in ArcGIS Pro—Excel | ArcGIS Desktop
2. By default table frames display the first 10 fields. You can remove or add fields as you want after inserting the table frame. Here is a link to the help topic that covers this topic - Add and modify table frames—Layouts | ArcGIS Desktop .
Here is the pertinent section:
Hope this helps,
Tom