Just got back from my trip and it was mostly a smooth experience. I arrived on Tuesday morning at 6am with about 25% SOC and headed to the top most covered floor as Yinn suggested. The first outlet I found worked just fine and no issues with the ground facing the "wrong" direction. I set my charge limit to 75%, plugged in and headed for the AirTrain.
A few hours before my departure time on my return day, I set the charge limit to 80% via the app and once I landed in EWR I turned on pre-conditioning. Arrived at P4 with my car charged at just under 80% SOC and a toasty 85F in the cabin.
My only hesitation is that I kind of felt like I was "stealing" electricity as its clear those outlets were not installed for EVs...I've heard anecdotal evidence that some airports (I think Logan) will ticket you if they find you're plugged into any 120V outlets at their garages. So its probably a matter of time before EWR does something similar.
In the future, I'll probably just take a Lyft or head to the
Kearny SuperCharger upon my arrival (once it comes online).
Also, if you are concerned about available parking spaces, you can check this site for data on parking capacity -->
Newark Airport.