Ok! I have been playing with your demo.
First issue is image point 0 should be middle.
also the else statement should be has inline of sight (inverted)
I also had to add set bullet angle of motion to sprite x,y on bullet enable to keep it from wandering off the screen.
as for the rotate 90/180 that works once image point 0 is middle,
But I changed that to set angle to player x,y for better response.