Nice explaination Normal, I did it the same myself. It works especially well to decoy with a Pz38 (I figured out quick that PzIV's do NOT make good decoys).
One thing I'd like to note, after taking the frontal arty batteries it will be easier to take out the tanks hiding in the town but still not a cake walk, I always kept one PzIV behind the "crest" until reinforcements arrive. Then with the perimeter secured I send in all my tanks at once to the bridge with cover from captured and reinforcement arty. Once the tanks get down to the bridge, the enemy arty and tanks in town don't have LOS, you can advance the town from the river as slowly as you want now, mortifying the infantry in their trenches. Yes, Dunkirk IS HARD but doable.
One last thing, how do you get snipers? I don't have any in my squads and dont see the option to "buy" any? Thanks!