The main Key Performance Indicators (KPIs) for the CMDB Health scorecard in ServiceNow include Correctness, Completeness, and Staleness. These KPIs are critical for assessing the overall health and quality of the CMDB. Correctness refers to the accuracy of the data in the CMDB, Completeness measures whether all required CI data is present, and Staleness indicates the freshness or timeliness of the CI data. Compliance and Duplicates, while important, are not considered main KPIs in the context of the CMDB Health scorecard.
References = ServiceNow CMDB documentation and CMDB Health Dashboard user guide, focusing on the key performance indicators for CMDB health.

File-based Discovery is a process that helps identify what software is running on your Windows and UNIX servers and devices, even if there is no registration information available. File-based Discovery is triggered in the exploration phase of normal Discovery, after the target device has been classified and identified. File-based Discovery probes execute a scan searching for specific file extensions or file names in paths that you configure. The resulting file information is returned in the probe payload. The sensor attempts to match the discovered files with installed software, using the file name, size, and version returned by the probe.
References: File-based Discovery, File Based Discovery - Support and Troubleshooting

The $process.executableDir expression correctly calls the value of the executableDir variable from the tabular process variable. The process variable is a tabular variable that contains the output of the ps command, which lists the processes running on a CI. The executableDir variable is a column name that holds the directory path of the executable file for each process. To access the value of a column name from a tabular variable, you need to use the dot notation, such as $variable.columnName12.
References
1: Pattern variables - Product Documentation: Tokyo - Now Support Portal
2: Examples of EVAL scripts used in Discovery patterns - ServiceNow