I am sure that your long post will be informative for others.
I have some comments.

I'm wondering if these variables could be at the project level for easier...

Not that I know of. Searching for FROM won't find JOINed tables, by the way.
Formatting your query better would make things a lot clearer:
1) Remove quotes
2) Use...

You're going to have to search the install log for errors. Without more info, this is impossible to diagnose at a distance.

If your source and destination tables are both on the same machine (which your initial post suggests), it would probably be a better idea to write a stored proc to...

If quantities get to 100 or more, you are likely to blow your max recursion limit & will need to use a different technique.

Some additional advice.
Add SET NOCOUNT ON.
I suggest you use DATE datatypes rather than DATETIME.
Use a temp table rather than a table variable – they usually perform better.

WITH summed
AS
(
  SELECT
   td.Chunk
  ,  NewChunk = SUM(IIF(td.LineNum = 1, 1, 0)) OVER (ORDER BY td.recid
                   ROWS UNBOUNDED PRECEDING
                 )
  FROM #tempData td