I looked up that sleeping bag, and it seems to have a somewhat unusually shaped stuff sack. You might consider a different stuff sack, and stuff your down jacket in with the bag to save some space, assuming you only use it in the evenings and mornings.

The MSR tent could be split between two or three people, as it's packed size is fairly large.

Three pairs of boxers seems unnecessary. I think that most people don't carry any extra underwear, other than long johns. Personally, I sometimes carry a pair of very lightweight briefs.

If you have the La Sportiva shoes, you could probably do without the flip-flops.

You definitely have to be a bit creative...my experience has been that I will fill to the brim whatever pack I have.
Always remember that you are absolutely unique, just like everybody else. -Margaret Mead