Can vertebral artery dissection cause slight bleed out or form hemotoma on exterior rather then within artery wall - if so, what could that cause?

Yes,not as above . Vertebral artery dissections can cause bleeding usually from the dissection/rupture of a saccular aneurysm. These aneurysms are more common intracranially than in the extracranial location. The aneurysms are typically located at branch points of the major vessel. Treatment of the aneurysm is typically endovascular, with the placement of coils to occlude the aneurysm.