Sure, but in the first example it's fight or flight, and in the case of being on top of a burning building, it's the fight response that would kick in, as well as shedloads of adrenalin. That's not overcoming SI in other words, that *is* SI that's giving you the strength to jump off the building, even though the chance of surviving the fall may be slim. I suspect bunny rabbits will just melt - they don't have much fight response, just a bit of nose wiggling lol
Scenario 2 - difficult one, and would very much depend on the person. A lot of people imho would take neither, and hope against all evidence that they could get the captors to release them. The human brain will do some very illogical things when faced with that kind of stress - stockholm syndrome, etc. There have been plenty of psychological experiments done on exactly this kind of scenario over the years, and none of them have humans come across as particularly sensible! Also of course not many people in that situation unless they already have suicidal ideation would even consider death to be a potential option.