i agree with all above, her asking you to shift to a day job is not cruelty, and is not a valid ground, however her constantly threatning to abandoning you over your inablity to secure a day job despite your sincere efforts to find one in compliance with your wife's request to such an extent that you are mentally stressed and you are put in a situation that you can neither live peacefully at home nor you are able to work properly at your office can be a valid ground for cruelty.
but i still feel courts might be sympathetic towards the wife and will not grant a divorce despite your efforts to prove cruelty,
better still she had to state that she was residing sepratly from you in her parents house to file a RCR, if she has stated in RCR that she left matrimonial home (your house) on her own due to your night shifts, then
since her RCR has failed, wait for 2 yrs from the from the date mentioned by her in RCR that she left your home to her parents home and file for divorce on the grounds of desertion. you still have to prove that you have taken considerable efforts to reconsile and she has refused to come without any valid reasons,(you working in night shifts is not a valid reason for her to leave you)
even better since RCR has failed you have a upper hand if she refuces you can apply for divorce, and she wont be eligable to apply for even maintanence, at this stage she cannot file 498 or DV as her RCR will be a proof aginst it,
talk to her parents and other elders and explain your sincere efforts to find a day job, and the circumstances in which you are not capable of finding it , if required explain her legal situation and try to persuade her
whatever you decide remember sometimes " a known devil is better than unknown angle"