Hi,
You doesn't qualify for PGWP anymore.
The only way to extend work permit is through LMO.
But you're left with only 3 months.
Step 1
Apply for restoration of status [From work permit to study permit]
step 2
After receiving study permit, start your education.
Step 3
While studying look for employer who can give you positive LMO.
Step 4
Either complete the studies and then apply for work permit through LMO
OR
Leave the studies in between and start working with LMO.
But anyhow you have to look for LMO before your study permit expires.
I hope you got it.
Good Luck