I doubt you can "make" your manager to do anything

I suggest that you have a discussion with your manager, tho, show both NOC descriptions and ask if they would be comfortable writing a letter that emphasizes the broker duties. Since your application is already in process, I suppose you're asking in case you need to re-apply...
For the LMO, as posted in this forum many times, for an employer to obtain an LMO for someone originally hired under the PGWP, there is no need to demonstrate recruitment efforts; the reason must be explicitly stated (originally hired on a PGWP), and they have to check "yes" when asked if 'intent to permanent." Supply a copy of the PGWP.
Show your employer this page (the important paragraph is the 2nd from the bottom).
http://www.hrsdc.gc.ca/eng/workplaceskills/foreign_workers/intstugrad.shtmlBut be warned, the position must be a skilled position... (6231), so you can discuss LMO and the Letter at the same time...