Is the Application (A) in Development environment or (B) a downstream environment where the Application has been deployed using a R-A-P?

With (B) you would start with the SystemManagement Service Package.  First run the "GET" RestorePoint Service with no id. Find the name of the restore point created when the R-A-P was installed. Next run the "POST" Rollback Service providing the restore point name (id). For attachLog say "true". For action say "SystemRollback".

Attempting (A) would be very complex if wanting to pin-point rules and data in shared tables that apply to one particular application and not others.  Data tables created specifically for the application would be simple to truncate.

If you have direct access to the database, perhaps through Connect-SQL rules, or can provide a script that a DBA  can execute (preferred), you can delete every row associated to a ruleset in your application regardless being a data class or a rule class.

Every database would have a way to search for columns by name regardless what table they are in.

For postgresql you would use:

select t.table_schema, t.table_name, c.column_name
from information_schema.tables t
inner join information_schema.columns c on c.table_name = t.table_name
                                and c.table_schema = t.table_schema
where c.column_name in ('pyrulesetname','pyruleset')
      and t.table_schema not in ('information_schema', 'pg_catalog')
      and t.table_type = 'BASE TABLE'
order by t.table_schema;

There are 100 tables in Pega 7.3.1.

In Excel, generate a delete statement for every table.

Plus generate a single-quoted, comma-delimited list of the rulesets in your Application by copying them from your Operator profile. 

The end goal is a statement for every table such as:

          DELETE FROM pr_operators WHERE pyRuleSetName IN ('Claim','ClaimInt','XYZ','XYZInt')

That should get the job done.