Your boss needs to write a letter to the Embassy. Don't take too seriously. Here are the KEY sentences in my 聘書for my J1 application.
"The aim of this project is to xxx. The duration of this project funded by xxxx will be at least two more years. Now he is applying for a waiver so that he may keep on the current research at xxx for this additional period ."
"I support Dr. xxx's application for a J1 waiver and the change of his visa from J-1 to H-1 by the United States Citizenship and Immigration Services."