I'll do my best to answer based on how I tailored my application, but this is just advice, take it or leave it
I would really push yourself to do better in your masters program in the upcoming science classes. Your grades aren't bad so far, but you really want to be getting As in these core classes. I do realize that's easier said than done, but try to analyze your study techniques and see if there's any room for improvement. What is your science GPA?
Your DAT isn't bad by any means, but it also a higher DAT score can somewhat make up for a lower GPA and other aspects of your application. If you can get your master's GPA higher by the time you complete it, then I wouldn't worry too much about retaking it. But something you might want to consider is retaking it, getting around a 21 AA and TS will help your case a lot.
Your extracurriculars are really solid, and you have way more shadowing hours than I had, I honestly probably would have pulled my hair out if I shadowed for 500 hours. I don't think you need to shadow as much anymore, I would just keep doing it periodically to show maintained interest in the profession.
Your volunteer work is great, just keep doing it when you can and make sure you have reasons to be there and are passionate about the projects, that really shines through in interviews when they bring it up. Maybe pick up a few dental related volunteering activities if you can find them to show you another side of the profession
