Oui, la différence est bien réelle dans la langue oral :) Cependant, tous les français ne l'accentuent pas autant ou pas de la même façon, selon les régions notamment.

You are pointing to the difference between è and é (et = è and er = é). For canadians, the difference is massive, but it's less pronounced for the French from France as they stess less on è that I would. For me, é is a small almost relax smile, sweet to pronounce (like english "ay") whereas è is a bigger "smile" (almost a grin) less pleasant sound (like in the word "merry", "gem" or "pet"). I hope this helps!

Pas vraiment. Tongue should go up a bit more on the er sound but dont count on that to recognize it.