Most of your questions can be answered here, and you can also sign up for a 7 day trial http://www.clikpic.com/ I would resize you images to 500px across, 72dpi before signing up though to get the most from the trial.
In answer to your other points:
It's easy to steal an image from any site. If I caught you using it though I would take all legal options available. The best that you can do is add a watermark across the image and make it low res as I have (72dpi/500px across). If someone really wants to they could remove the watermark I guess, but I don't think anyone would seriuously go to that trouble with a low res image.
I've had quite a few thousand hits on my site but no sales. The site itself won't generate sales. m Keywords won't generate sales. YOU have to generate the sales. You don't get passing foot traffic with a website, peopel have to be directed there so it's up to you to advertise it if you really want sales from it.
It costs about £35 a year for 60 photos, I've just upped it to £45 for 120 photos. This includes the paypal shopping cart.
It's dead easy to update the site. You log in, add images, change text etc. Then when you are ready you "make live".
There are lots of templates available and you can change fonts and sizes to suit your needs. It takes some trial and error but as I say, you can preview teh site and then make live later.
There are tonnes of options out there, Shelfy's is a good example of another. As I say though, don't expect to build a site and have the sales roll in. It doesn't work like that!
