He doesn't automatically stop saving people. He eventually loses his will to do so (some kind of depression) because the giant hole left by not knowing his alien heritage which he desperately longs for is starting to take it's tole on him as a man (basic identity crisis) because he lacks that closure. This would lead to him having thoughts of wanting to forget that side of him all together because it makes him feel as if though he was a mistake, unwanted, neglected etc. due to no follow up by his parents/people and progress in uncovering the reason he was sent to earth. He wants to disappear into the Clark Kent persona (glasses, hair, clumsiness etc...... In this case he wouldn't use his real name and would fake an identity seeing he didn't plan to stay their forever....second paragraph addresses why
) which at first he basically viewed as a temporary act to fit in among humans to aid in uncovering the truth about himself with little suspicion. With this premise you can at least kinda buy into him not being recognized because he could make a conscious effort to conceal his identity when being heroic (shades,hat,shirt tied around his head etc.) because he has to keep up with appearances. Also the reason he won't openly expose himself to the world would not be because Pa Kent felt that the world wasn't ready, but because Clark himself is reluctant due to being unsure of who he's supposed to be as an individual. This way it could have have been a more self centered choice after his breakthrough (made possible by Lois and not magical coincidence) to reveal himself and no longer hold back the hero in him other than being forced out by Zod. This way the heroic side of him is truly preserved and is only affected and conflicted due to him (the man) longing for a true identity and not knowing who he was. Wouldn't this make the story more focused on the character who should be the driving force of the story?
With regards to how he would regain continue to work at DP after revealing himself is another story. I really don't know how the glasses could ever realistically translate to a grounded universe which is why the identity crisis angle would be a little more plausible. Before revealing himself, Clark was struggling with his identity so he wouldn't even use his real name (Clark) before this and would go to great ends to preserve his natural appearance. Maybe this is where a fake beard, mustache and fake tan would come in handy as well as maybe using heat vision and an iron comb to flatten and straighten his hair while walking differently etc.
Desperate times call for desperate measures. This would give him a totally different look. When he finally isn't unsure of who he is anymore and gets a new job at DP post crisis, all the theatrics are in the past and he can now be the real Clark Kent with the name. This would show his progression as a character and be symbolic of his new found sense of self, purpose and confidence. The other question now is why risk it and go back to DP which my answer is....because of Lois Lane along with basically the same reason offered at the end of MOS.