Hi!
You were right, I managed to delete a single cell when reordered the maps and it made it impossible to finish it... Doh!
I have uploaded an updated version, it will be obvious which cell was missing...
In any case, as strategy for that screen (for me it was only 4 missing fire charges to complete the screen) you must first accumulate as much ammo as you can, and be careful using the wipes as these are the only ones that can destroy rock. Also, sometimes what may look like a waste of ammo when reviewed twice can turn into more ammo available.
Finally, about the levels, there are 20 levels, so you have already played more than a half of the game.
Hope you enjoy it, and if you find any other problem please let me know :)