Since he could absorb all the cosmic energies from the stars? Like would his powers be at his peak there

See to me its still the same, his body can only hold so much energy anyway. Being in space shouldn't make him able to hold any more energy than he does on Earth. And there's no indication that the cosmic energy he absorbs is hindered by Earth's atmosphere so he should still absorb it at the same rate.

can he only control it after it's in his body. or can he control it raw?

"See to me its still the same, his body can only hold so much energy anyway. Being in space shouldn't make him able to hold any more energy than he does on Earth. And there's no indication that the cosmic energy he absorbs is hindered by Earth's atmosphere so he should still absorb it at the same rate."

Real-world cosmic rays are heavily dispersed by the atmosphere, and are also blocked by the planet itself.  Only extremely long wavelength rays can pass through something the size of the Earth.
 
However, if Havok is a cosmic 'antenna', he'd actually alter the shape of the local cosmic field, and would bend rays toward himself regardless of whether he were in an atmosphere, space ship, or total vacuum.

My common sense tells me that he would be stronger in space.

@IKnowEverything said:

My common sense tells me that he would be stronger in space.

He may just have Superman Syndrome, where he severely hinders himself when he's around civilization.

Yes they do work best in space. Go read Uncanny XMen story. Havok & Prof X chase Vulcan into space & after Vulcan becomes the Shi’ar Emperor.

Havok IMO uses his powers to their max here, he absorbs energy from a star and becomes hella strong

Yes they do work best in space. Go read Uncanny XMen story. Havok & Prof X chase Vulcan into space & after Vulcan becomes the Shi’ar Emperor.

Havok IMO uses his powers to their max here, he absorbs energy from a star and becomes hella strong