Same Day Change won't apply on DUB to IAD sectors, it's only on single trips on CE (with a few exceptions) and only within Europe / North Africa. To move the DUB flight will almost certainly entail a change fee - which should have been visible at the time of booking - and a fare difference, probably approaching a king's ransom on the first leg. So I think that's a no go. Given you have the singular advantage of an overnight stay, I would very much suggest you take all luggage to DUB, and then check it on the morning service, rather than find yourself in potential difficulties on connections. There are left luggage facilities in DUB by the Spar in T1 landside towards the carpark.

Alternatively use the left luggage shop in Arrivals by Marks and Spencer, particularly if you have First Wing access (and perhaps still if you have just vanilla Fast Track), since from DUB it won't make much difference to the connection timings compared to airside Flight Connections. If you miss the booked IAD flight due to a connection that falls so short then I'm reasonably confident they would rebook you on to the next available IAD service,