"You" (spouse #2) can't contribute to spouse #1's DCFSA. Only spouse #1 can contribute, through a section 125 cafeteria plan offered by employer #1.
Spouse #2 can contribute to a separate DCFSA at spouse #2's employer, if offered. The maximum overall contribution for both spouses combined is still $5000. The limitation on spouse #1 does not affect spouse #2 if spouse #2 is eligible through employer #2.
