1. UA isn't going to do anything to compensate you in WX, especially not for train tickets, car rental and the like.

2. Fastest and easiest way to IAD from EWR is a one-way car rental. Amtrak seems convenient, but it drops you at Union Station with a cab ride out to IAD. WX in the DC area is just fine right now. If the roads to the north are OK, I would grab this and run.

3. Getting rebooked onto another carrier is much easier at the airport than over the phone. Airport agents can see the line below you and just do stuff which they probably should not. Phone agents are more likely to follow the rules. On the other hand, given massive IRROPS in the northeast, grabbing revenue seats for awards from another carrier (*A or not) may be tough because each carrier already has its own pax to take care of. This process also takes time.