It would not be advisable to withdraw your paper at such an advanced stage. Generally, papers that receive minor revisions have higher chances of acceptance. Additionally, the fact that the status date is changing shows that the editor is chceking your paper from time to time to see if the reviewer comments have come in. This means that the editor is taking an interest in your submission.
Moreover, if you withdraw and submit the paper to another journal, the entire journal evaluation process will start from scratch once again, and might take even longer to complete. Unfortunately, the peer review process, for most journals, is rather time-consuming.
Since you have already waited for so long, you might as well wait a few more weeks. Once the reviewer sends in his or her comments, it should not take too long. However, you should follow up with the journal editor more fequently now. Perhaps you can write to the editor once again after a week explaining that your graduation is dependent on this publication, and request him/her to expedite the process if possible.