Your dentistry clinical hours really won't help you. Try shadowing physicians to help you out there or volunteer in the clinical setting.
Also, DO/PhD is fairly uncommon from what I understand. You will really limit yourselves as to what schools you can apply to if you're wanting to do the combined degree program (I honestly don't even remember seeing one when I was researching schools), which is not something you want to do when applying. You need to apply broadly if you are concerned about your chances. So the MD route is probably your best bet, but the 3.35 cum GPA might hurt you, so I would recommend retaking the classes you didn't do well in, or taking more classes to boost the GPA. If you really kill the MCAT (30+) you should be in good shape, as long as the rest of your application is beefed up and your LORs are solid. Good luck! 🙂