What I'd do would be to look at the 10:30 redeye out of SFO to
CLT, connecting perhaps to FLL and then Ted to DEN.
I don't know if this can be booked as UA numbers and even if
so whether your voucher would be usable, but I'd save the
voucher for next year and take, say:
1109 SFO CLT US 784
1110 CLT FLL US 989
1110 FLL DEN UA1531
On Orbitz, 14 hrs, $335 a/i.