Lost Job on last-but-one day of my OPT with STEM extension application pending. What are my options?

I was working with one reputed organisation where my employment was terminated(July 2) on a day before my OPT end date(July 3). I have filed my STEM OPT Extension application with the USCIS on May 21st and is still pending with them. I do not have another offer at hand and I am unable to perform in the interviews carrying all these status worries. I have a few questions precisely. * What will happen if I report the termination of employment to the DSO late (like after I receive my EAD with STEM Extension). I know there is a rule that I have to report with in 10 days of employment status change. * What will happen if I did update the DSO with the termination of employment. Will that cancel my existing STEM OPT application with USCIS? * How many days of unemployment will I be allowed to search the new job.(I have 23 left on OPT)

I couldn't risk asking all these questions to the DSO myself as my college DSO are very strict and they document every conversation.

I have very less time, so any help opinion in this regard is appreciated.