1. The whole point of volunteer hours are to show them that you have exposure to the PT profession under the supervision of a PT. Technically, if you weren't specifically observing under a PT, it would not count. (However, if the PT on your team agrees to fill out the hours form saying that he was your supervising PT, I don't see why it can't be done..)
2. No. You'll get in somewhere if you apply to a number of schools.
3. Yes. Especially considering your masters and exercise physiologist background. However, observation hours in different PT specialties would help.
4. This is the problem. IMO 200k is too much.
5. Pretty sure there isn't any.
You are going to be suffering from debt when you get out of the school and may even feel like you've made a wrong decision, but your income potential definitely will be higher w/ experience.
If you see yourself doing this for the rest of your life, I say why not.
However, weigh the opportunity costs of you not working 3 years (150k), the debt, age, etc. It'll take some time to break even.
That said, you are probably in your mid to late 20s.
If you want to to actually go to PT school, now is the time. Not later.
Good luck.
