Depending on the brand, we've seen varying degrees of knee loop angles. Some are close to 90 degrees from vertical, and others have a slight downward angle beyond 90 degrees. But whichever, they both should be the same on a single pair of risers. Both slightly downward really makes no difference. Typically, new owners will take risers out of the box and want to see how strong the spring is -- so they hold a riser upright and push their weight down on the knee loop to see how much they can flex the spring.
Yeah... I did that, too.

Well, I was lucky. My loop didn't bend. One thing about the original Powerisers is that they used pretty strong aluminum in the knee loops. But I know some other models can bend pretty easily, so if you did the newbie of the box spring flex thing -- well, the knee loop probably bent a little and you didn't notice it at the time. With a little careful pulling, you can probably bend it back. Or bend the other one down a little. But do it GRADUALLY. There have been cases where bending and torquing the the loop a little too much has caused the aluminum tubing to actually snap.
As far as breaking in the springs, it will depend on how often you use them. Taking into account that you are at the lower end of your weight range, I'd guess it might take you about a month of regular use to break in the springs. Naturally, going really easy on them and just walking around and not jumping would make it take longer. Other opinions are welcome.
Hope that helps.
Bill C.