I can confirm that it indeed works on Windows. Adjusting the lunchbox number is also very easy.
1) Download the FOSDecrypt.exe file, put the .sav file into the same folder
2) Drag the Vault1.sav file (Or Vault2.sav, or Vault3.sav, whatever your Vault save file is) ONTO the .exe file, then let it go. ** Now, FOSDecrypt decrypts the file into a readable format
3) EDIT the file as you want
4) Do the same thing as in 2) again, drag the Vault save file onto FOSDecrypt. The save file needs to be encrypted for the game to be able to process it again.
If you want to edit your lunchboxes, search for LunchBoxesByType and LunchBoxesCount. There is a pair of square brackets after LunchBoxesByType.
0 is for a regular Lunchbox, 1 is for Mr. Handy boxes. For each box that you want, add a 0 or 1, separated by a comma. So, if you want to add 10 boxes each, your square bracket content would be [0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1]. Obviously, you'll need to adjust the LunchBoxesCount as to how many boxes you added.