Johnny, It is important to read the following posts carefully (if you are really interested in this particular subject):
What Is a Wave and What Is a Particle?
Photons Are Particles Not Waves
Contrary to what you learned in the old days (as we all did), light is not a wave. Light is a stream of particles called photons. Don’t feel bad. I know some physicists who still think of light as a wave. It is very important to understand the difference between a wave and a wave function, as discussed in the first three posts.
After reading the above posts carefully, also read #10 of the new post. There I point out that the observation of zero signal with experiments done with large plate thicknesses again disprove light is a wave, for the same reasons that you pointed out (#1 off of the top surface is gone even before #2 coming from the bottom surface gets there; thus destructive interference of “waves” cannot happen).
P.S. Of course many phenomena involving light can be explained with light treated as an electromagnetic wave, just like the motion of large particles can be treated with Newtonian mechanics.
But when analyzing quantum phenomena, neither the EM theory nor the Newtonian mechanics work.