1. Correct as is.
2. Correct as is.
3. Correct as is. (Either works)
4. I got 2nd degree burns as a child.
5. Correct as is.
6. Correct as is.
7. Comma splice. (A period, colon, or semicolon is needed; not sure which.)
I am not entirely sure, but I think those are the only corrections you need.