Depends on the job you're doing, too. If you think it's making you more compelling as a candidate, you probably want to stick with it. On the other hand, if it doesn't do so and also doesn't allow you enough time to volunteer or do research to strengthen your application, that makes full-time study more compelling.
The good thing for you is that you already have grades from four science credits and an overall GPA that can help you with you decision. Do you feel like you're strongly on track to get the kind of grades you need to get into med schools? If so, I'd say that pushes you towards full-time study, since the risk is lower: you'd take on debt, but you'd get into med school earlier, which means you'd start earning a physician's salary earlier. Your financial loss from one year of debt/no work would be outweighed by working as a physician one year sooner (100k in debt/lost earnings versus 170k or so as a fresh attending).
If you feel like you might struggle to get into med school, then minimizing debt might be a greater priority. What's more, taking things slower might gain you life experiences that would allow you to balance a weaker set of scores.
Finally, do you feel that you're in an environment to succeed during part-time study? I've worked plenty of 100-hour week jobs, so I know that certain circumstances make it hard to juggle work and study. If you don't think you can get As while working, you need to either find another (easier) job or go full-time, no ifs and buts.
