Actually I am not home so I can't open your project, sorry.
What about creating an event that ends the level when the object count of all types of enemies is 0? Something like this (multiple conditions single event):
|Enemy1.count is 0 | [*End level*]
|enemy2.count is 0 |
|enemy3.count is 0 |
|enemy4.count is 0 |
If that will not work for you, I'll try to edit your .capx file in the afternoon