On function level up
Set creature size
width to creature.width*100
height to creature.height*100
I am assuming you want the camera to grow with the creature? If so
Set canvas size to canvas size*100
The enemy thing is a bit more complicated however you might want to include a instance variable for your level. On enemy spawn function if the spawn is at least 2 off your level (so if you are level 5 it would be 3, 4, 5, 6 and 7 enemies that could spawn)