Your stats and EC’s definitely qualify you for those schools, and your childhood will make for a powerful, powerful essay.
The B+ won’t hurt you at all!
One thing- It’s clear that you worked very hard and committed to an incredible amount of EC’s. However, I worry about the focus of your EC’s. If you’re focusing them to back you up on a major choice, it’s not clear. If you’re not sure about major choice yet, then don’t worry and disregard me!