Hi! so to my understanding, you want to visit back home in December 2022, but your TRV expires by August 31st.
Unfortunately, you won't be able to get a new TRV until your PGWP is approved. Hopefully, May 2022 PGWP applicants will receive their approvals by September considering the current rate of application processing. You need a TRV in order to re-enter Canada, so in my opinion you have to wait to apply for it until the PGWP is approved. Good luck!