From what I can recall, I don't believe there is a certain amount of hours you need to shadow. I had like 15 hours of shadowing.
You don't necessarily need the LORs at the time of applying. Most schools look at your GPA and MCAT numbers first. However, with scholl, they will need your LORs before they make their decision. Overall, it will be easier for you if you just submit everything together (if LOR is going to delay your application, then I suggest submitting app first, then LORs later)
Your sGPA and cGPA is quite nice. However, the issue I see is your MCAT score. 490 is a low score ( I believe it's like a 19 on the old mcat). With my experience so far, schools are putting a heavy emphasis on the MCAT scores. With DMU and Scholl, you might need to retake it. I suggest calling the schools and see what your chances are.
I've seen people get some interviews with lower numbers than yours, so you might have a chance. I suggest applying to the bigger schools as well (4 big schools are kent state, scholl, nycpm, and temple). Also, I suggest not applying to temple unless you can get your mcat score past 495 or even 500+.