Absolutely, you can say all you mentioned. " Killed it" is a slang phrase used for something that was done to a near perfection. Like you nailed it !! So if you scored 100% on a big English test you can say, I killed it !!. If you had a motorcycle race or bike race and you won, or did great, you can say, I killed it !! You ran a obstacle course in record time, you can tell your friends, I killed it !!! It's an expression of self enthusiasm for a successful completion of a difficult task...

You are correct, it means he performed it (jumping over 6 buses) perfectly/impressively. Other phrases are "You nailed it" "You smashed it" Yes you can say he killed it, she killed it, I killed it or we killed It.