Why did you change the query to dynamic? There's a potentially very good reason...

Here's the query formatted for readability. I'm not prepared to go any further with this,...

-- I find it helps to preaggregate the table down BEFORE the pivot.
-- it's a visual thing - it's easier to see what's going to happen.

SELECT @dtStart =

Something like this:
SELECT cus.CompanyName, kc.SalesItemId,
 SUM([Solgt i perioden KG]),
 SUM([Ultimo lager KG]),
 SUM([Primo lager KG]),
 SUM([Købt i perioden KG]),
 SUM([Solgt i perioden KG])

FROM [dbo].[CustomerSetup] cus
LEFT JOIN...

You're writing a "dynamic cross-tab query". It's well-documented and very well studied.
To begin with, can you write the query you would need for just the first percent column,...