That's a really nice demonstration on the sudoku's sticking point. I caught the same simple step when I solved it after the test. Often my eye catches the right digit to search, but not the simplest way to find use it (fastest, but not simplest). Here I failed to have the existing note in column 9 about a 9 in box 6, but reconstructed what I needed from just considering the effect of a 9 in R9C7 (which is bad!).
My approach on the Gapped Kakuro was actually center before left, which meant I didn't have the benefit of knowing the 6 in the middle row.
What I noticed is that the columns of 40 and 43 mean that you need two 9s and two 7s in those columns. The 16 accounts for one of each, and the 15 accounts for at most one of the other. So where's the fourth? It turns out you can eliminate it from all the rows except for the 2-cell 9 clue -- and putting the 7 there leads to a contradiction.