Persoanlly, would not book a 1 hour connection at EWR on a single ticket, much less separate ones (mote: from someone who used to book 40-minute domestic connections at ORD all the time). Yes, agent at DCA can through-check, but that is the least of your worries. I give myself a two hour minimum at EWR (though might give a little more wiggle room on this first thing in the morning, but still not an hour), but that would be on a single ticket. Definitely arrive at EWR the night before.