Using SQL Server to check for file existence from within an SSIS package seems inelegant.
Have you considered creating a script task to do this?
It's very easy in C#...

Are the N1–N7 column headings fixed or dynamic?

So ... declare it, or use literal text if it's always the same!
I did not give you my code it its entirety, you'll have to fill in a...

The double quotes method seems to work, while using single quotes does not, which is interesting.

DROP TABLE IF EXISTS #garbage;

CREATE TABLE #garbage
(
 ...

So is your package as simple as just a
truncate target
followed by a simple source/target dataflow?

Or does it contain any other transformations?

Can you post the results of running 'SCRIPT TABLE AS CREATE'  please?

Does your target table contain any indexes or keys (primary or foreign)?