It shouldn't be a surprise that it is very hard to keep humans alive outside the exact environment we evolved in. Current squishy humans will never colonize space, only intelligences using a vastly more durable substrate will be able to.
I suspect so, but I wouldn't want to bet on it.
Enough humans seem to be repelled by the idea of transhumanism that they may well insist on doing it the hard way.
you get it exactly
I do like the theory of using a massive amount of water to surround a ship as a shield, it solves a lot of radiation problems and something humans desperately need for long travel (with super-recycling) but not a solution once you get there
and we'll definitely have super-advanced space-drones, eventually