The easiest solution would be to put the cream cheese in a "toiletry" container in the toiletry ziploc, or get a little single-serving cream cheese packet. I would imagine that cream cheese or butter could be misconstrued as a "gel" by a cranky TSA agent, and the system pretty much gives them the final word regardless of the current regulations.

I have actually taken cupcakes through without issue (despite the frosting) but always expect problems.

I agree with you on the food options at Dulles. I was stuck there once for 5 hours (from 5:20 am to about 10) waiting for a flight to Richmond. My terminal was surprisingly deserted at 5 am.