It's not just the advertising that has to be completed before your employer can apply for the LMIA. They have to evaluate the applications, interview potential applicants, and then make a determination that there is no Canadian who can do the job. Then they can submit an LMIA application.
So, in other words, it will not be possible for your employer to submit a valid LMIA application in time to allow you to keep working under implied status. You will likely either have to change to visitor status, orleave Canada while the LMIA and work permit applications are pending.
What is your country of citizenship? You could look into IEC permits, it may be a faster way to come back and start working than waiting for the LMIA (But the LMIA, if approved, will allow you to claim 50 pts for a valid job offer...)
PGWP are not extendable so you wouldn't qualify for any bridging program.