Unable to insert line break or carriage return in mail merge field

[macropod]

It's not apparent to me why you'd be creating the document from scratch every time instead of using a document or template with the required fields already in place. That would require much less code and would be far easier to maintain.

As for changing a mergefield's output from:
Value1 Value2 Value3
to:
Value1
Value2
Value3
there is no mergefield coding that can produce such a result.