I'm just thinking-Supes gains his powers through the Sun_ which is filtered by the atmosphere on Earth. If in space, There's more electromagnetic energy for Superman to absorb. Is this true, or just a thought?

definitely true,the closer he gets to the sun,the more energy his body will absorb.

But he needs to breathe,and is adjusted to this atmosphere,which is why he is mostly a earth based hero,not universe based hero.

He doesn't need to breath or adjust to anything, Earth's his home and the GL's protect the Universe, so he only goes into space when he has to.

Breathing in space has been a on again,off again ability for Superman for decades,where he lands in the new 52 is up in the air,but he has tracked Starfire's ship.

I think Superman should still need oxygen, water, and food... but could last much longer without it than humans.

You cannot breathe in space, there is no air to breathe. Space is a vacuum.

But yes, the Earth's atmosphere filters the UV rays, making the strength of the radiation weaker. So if he leaves the atmosphere, he becomes theoretically stronger.

Yeah that's true,no breathing in space,more not having a need for it.new 52 kryptonians,even superboy who is a hybrid,all have bodies that need no food,drink,or sleep.

wouldn't it not be about "needing" anything, including endurance, but more about how space vaccuum literally sucks out every inch of oxygen inside your body, absolute zero temperatures maybe his body can resist for long, but the gas difference should surely cause any "kept" oxygen to just immediately leave?