There isn't a "correct" answer to this question. A person can effectively answer either side of whether or not Sammy made the right decision in quitting his job. I think a strong argument could be that Sammy made the wrong decision, because it didn't gain him what he hoped it would. Additionally, the motivation behind his choice was selfish and not at all chivalrous.
Sammy might believe that his decision is based on some desire to protect the girls in the store. Maybe he believes he is protecting them, because they are women. Maybe he believes he's protecting them against Lengel and Lengel's cold enforcement of rules. Perhaps Sammy thinks that by quitting, he is making a statement against sexism, and the girls will appreciate his bold stance. Each of those beliefs is not true. Sammy quits his job for selfish reasons. Sammy quits because he believes his actions will be viewed as heroic by the girls. Sammy especially wants Queenie to see him as heroic, which will allow him to move up social and economic ladders as he becomes part of her life.
While Sammy's reasons are selfish and not intended to benefit the girls, the real reason that Sammy's decision is the wrong decision is because it doesn't benefit him in any way. If Sammy's decision had made him Queenie's dream man, one could make the argument that his decision was the right one, because it benefited Sammy in the way that he hoped it would. Unfortunately for Sammy, the girls don't notice his actions. He's just as unnoticed by them as before. Additionally, he doesn't have a job anymore, which puts him in a tougher financial position than before. He doesn't have the job. He doesn't have the money. He doesn't have the girl. He's alone and soon to be broke. Sammy made the wrong decision.