1. Enough armor can reduce space radiation to Earth levels, or even lower. And protect against space junk. It's just currently expensive to launch. 2. Spinning

1. Enough armor can reduce space radiation to Earth levels, or even lower. And protect against space junk. It's just currently expensive to launch. 2. Spinning habitats create artificial gravity (though astronauts on the ISS do okay in zero g for months or more). No new tech advances necessary. Humans are nothing if not adaptable and ingenious. Space is just next in a long line of "inhospitable" areas we've colonized.