Absolutely fantastic work!
On a side note, you do not need a fresh account for this hack to work. Looking at the mission file, it's clear that the rewards are set for each mission, there are two variations:rewards for the first time you clear it(match_reward_first_win) and rewards for each subsequent clear (match_reward_win)
Tweaking the currency values and xp for the match_reward_first_win will alter your rewards for your first time clearing it. However, altering values for match_reward_win will alter the values for the rewards for missions you have already cleared.
Meaning that if you alter the rewards for a normal clear, you can just do that mission over and over to get more coins/crystals.
Another note is that 50000 is a safe number, anything too big will not work.
Surprisingly, currency type can also be manipulated, by simply changing currency_soft to currecy_hard, you can obtain crystals as rewards where you would normals get bytecoins.