Ready to purchase my first chastity device, what should I expect? What should I get? Any advice is appreciated.

I've been a fan of chastity for some time, but I've never owned a device before. I'm looking to purchase a comfortable, discrete device for >$100. My penis is fairly large, 6.5 inches erect and around 3.5 soft. I've been exploring getting a device for some time, but I see a lot of varying doubletalk and inconsistent reviews, so any advice would be greatly appreciated!

My main questions:

1. What are the some of the best chastity devices on the market? I was hoping to spend under a hundred dollars, but if a device is worth it, I can spare more money.
2. What are some ways to deal with pain/discomfort?
3. How can I insure my emergency key is never lost?
4. In case I were to lose the key, god forbid, what should I do?
5. Exercise with the device: Is it feasible?
6. What are the logistics of long distance keyholding? Is it feasible? Is it desirable?
7. Is there any physical harm to going longer than, say, 2 weeks at a time? At what point is chastity dangerous?
8. Any general advice for keeping the device imperceptible? I'm not shy, but I'd rather not have to start every conversation with "Hi, I'm Smart_Pet! Oh, that buldge you're seeing? Don't worry, I'm just debasing myself sexually because that's what does the trick for me, how was your weekend?"

Thanks in advance for the advice, I know I'm not the only one who would benefit tremendously from getting these questions answered.