Get (FoundCount) will only get the current count of the current found set. You are setting a few things to the same found number.
...count the occurrences of a specific incident (incident category) related to that Entity and also provide the number of occurrences for that Incident.
Are not these two things exactly the same?
Will something like this work:
Set Variable[ $count; Value: If ( IsEmpty ( Count ( Table::IncidentID ) ) ; 0 ; Count ( Table::IncidentID ) )]
Provides you with the number of related Incident records to the Entity by relationship. If you want to count how many of those records are marked with a "yes" flag that is a little different, but possible.
What do you mean by List? Are you using portals?