Let's see if I can help.
The top card is a UX19. Used catalog value is $0.50.
The bottom card is a UX27. Used catalog value is $0.25.
The fact that the reverse of the cards may be printed upside down is not really an issue, as these cards were supplied blank and the companies using them proceeded to print whatever they desired on the back (and oftentimes they did inadvertently print them upside down).
As for the postmark on the top card, you are probably right that it's 1909. Those older flag cancellations typically had the year as "19" and "09" separated apart as in this example:

The poorly inked lower right side of the circular part of the postmark would suggest that it simply did not adhere to the postal card. It is interesting that the reverse of the card suggests a January 1st due date, but it also suggests that a discount were available if it were paid before January 10th, so they were probably just sent out late, as the recipient did have time to make a timely payment by January 10th.