Exactly what part are you having trouble with? The Find, or the summary fields?
The summary fields are showing what I want for overall summary without time restriction.
I commented out the report part and tried the script for the Find part. It seems that the script did not perform find as I think it should.
1. Perform the find on the report layout itself
2. We cannot see your search conditions; it usually better to use Enter Find Mode / Set Field (or fields, with your search criteria) / Perform Find, so you don't have to open the dialog to see all option.
3. If tablename_startDate are globals and you want to use them as is, you don't need to put them into variables (unless you need them more than once), since they're accessible from everywhere.
4. Don't use Halt Script, unless you explicitly want to prevent the script to return to a calling script; use Exit Script
In brief, try …
Go to Layout [ REPORT- Age ; someTO ) ]
Enter Find Mode [ no pause ]
Set Field [ someTO::date ; tableName::startDate & ".." & tableName::endDate ]
# other criteria …
Set Error Capture [ On ]
If [ not Get ( FoundCount ) ]
Close Window (??)
Sort [ as per sub-summary definition )
In general, it's best to show a complete script, incl. dependencies (calling script / sub-scripts).
You can print a script by pressing Cmd/Ctr-P; in OS X, you can open a preview in … well, Preview, then copy the script text. This version also shows the “invisible” dialog options mentioned above; great for pasting when posting.