hmmm, seems like youve got it covered really, especially the upper body stuff. as long as you are training reguarly and im sure you are, then its more than likely 'on the day' something wasnt there.
did you actually 'struggle' with the ladder sim or was it your grip or something else they picked you up on?
all i would suggest for your program would be to try and up the weight on d'bell shoulder press considerably. throw in some bicep curls (the initial part of the sim requires a bicep movement if i remember correctly) and if poss, do some wide grip chins and some squats (with a bar) these are better overall strength moves.
if you have access to a gym or have decent weights at home, try a 'hang/clean to press' movement with the bar, this mimics the test more accurately than a shoulder press for example.
try and lift reasonably high weight for less reps (6 is good after a warm up) to improve strength, you are only required to lift the ladder once in the test so doing high reps at lower weight will not bring you results.
hope this helps and good luck!