There isn't an easy way I'm afraid. What could be the solution is the following.
You take the content from your header "Fake company...." and content from thead and move it to the extra template.
Then you merge this extra template into the main one using pdf utils. This will provide you the same result as you have now, but opens the door to use pdf utils pages group to calculate the dynamic value you want to have at the beginning of every page.
See this example
https://playground.jsreport.net/w/admin/k1fGHFZp
And pdf utils documentation
https://jsreport.net/learn/pdf-utils