Yeah, they don't need hydrocarbon fuel, they're starting with energy from somewhere else anyway to initially make the oxygen. Just continue to use that energy source(possibly storing energy with hydrocarbons).

The 12mph collision would still be done in a space suit. Hopefully the space suit has a solid combination of rigidity and cushioning to protect against that level of fall. Sinking in to a memory foam and not being able to twist limbs or necks in to bad positions sounds good.