Cryostasis units. People can be cryogenically frozen and preserved like that for long periods of time.

[ Which would make sense if they happened to go on long hibernation periods while traveling across space, but they don't. But he'll save his issues and concerns with the cryostasis system on board the Moira for himself. ]

There are. Bow defense specialists basically man the weapons and defense systems on the ship. Steve works there, too. Then you have personal defense specialists, people who train others in defense techniques, fighting styles, weaponry and the like. That's what Natasha does.