meh i have overnighted a number of times at ewr. typically sleep near the end of the concourse with the international flights, i think it's around gate 130 or something like that. i just sleep on the floor in some corner where i'm not easily visible, and nobody has ever bothered me.
it's ok, not particularly comfortable, but i would feel absurd getting a hotel for 3 hours or whatever.
The OP did say they would have 10 1/2 hrs between flights 9pm arrival , 7:30am departure.
No way would I spend that amount of time in EWR, as others have suggested PL a Hotel room or cash in some pts