I went on usair.com and used the Multi City feature to create the following:
SFO-DUB 12/13
DUB-PHL-IAD 12/14 (immediate turn-around from the previous red-eye flight)
IAD-LAS-SFO 12/15
For $646 all in.
I actually like the US website and how it distinguishes each segment by a $ amount so I can pick the cheapest ones. This was especially true for the IAD-SFO segment, there were many choices that were over $1000, but then 2 for only $114.
I don't know if those are the dates you were going for, but for the bonus you're talking about, you might want to try again.