Yes, there's a limit to how much content you can store in a content control's value. For longer content, you can use custom document variables instead. For some code that does that, see:
https://www.msofficeforums.com/word-...tml#post119230. The code in that post also gets the variable content from Excel, but that may or may not be relevant to your requirements. The important thing to not is how the document variables are used.