Is it sane, given foreknowledge of your own demise and the power to avert it, to charge full-steam-ahead toward that demise
It's not my demise; it is the demise of others, sometime in the future. I fully expect to live out the rest of my life comfortably. I rather suspect that's the same set of conditions you face when you describe these worst case scenarios to others. Some of us are sensitive to the woes of future persons, some of us are not. But it's always at least one step removed from today's reality.
In the USA, just look at the number of people who would let the financially low performing suffer the slings and arrows of disease and injury without any particular concern or guilt; you can measure that directly by the resistance to the ACA, which remains substantial, even though it's working out pretty well if you actually take the time to look at the numbers. When people don't concern themselves with the other people in town, who are there and suffering right now, isn't it a bit optimistic to expect them to concern themselves with some abstract, unknown set of people who will exist after most of them have died anyway?
You're better off looking to technology to solve this than compassionate outlooks among the citizenry.
I'm going to go back to watching the news now, where I can learn more about us shooting up Afghanistan for no particular reason other than to prop up our MI complex, as we've kind of worn out Iraq now. You know, because we care. We'd be in Africa "helping" them too, you know, if we needed more income. I'm sure their day will come, though. Both Africa and South America are deep future market resources for our weapons manufacturers. Caring. It's what we do!