what exactly do you mean by interaction strenght ? i thought gravity pulled depending on mass, so a more massive object will be more subject to it ? thats why the moon revolves and a comet just slings by ?

When there is a dark sector, they may come with their own set of interactions that are different from the fundamental ones we know. Those interactions may have different strength. Not electromagnetic, not weak, not strong. Just a different one.

I hope this short answer clarifies.