p.s.  You didn't make the mistake of shrinking your database files, did you?

Before you try anything, you said this problem started recently.  The first thing you should do is make sure your statistics are up do date.

This is also an...

While I appreciate some of the technical aspects of the script, silently dropping existing views scares the heck out of me.  I'd recommend adding a parameter that would default to...

Ah... Just noticed that you're using 2014.  The VLF algorithm changed there.  See the following article...
https://www.sqlskills.com/blogs/paul/important-change-vlf-creation-algorithm-sql-server-2014/

The bottom line, though, is that growing by percent is still...

I'm not sure why you have so much free space for the NDF files.  Something is wrong there or you've measured something wrong or it's used space and not free...

p.s.  If your new requirement is to truncate the whole table and then reload it, it's almost stupid for the table to be partitioned.  It's buying you very little and may...

Just to add a bit about performance, most of the performance is in the code when applied to a correctly indexed table.  If you have code that is generated by...