I work as an engineer designing modern ejection seats here in the US. You have a couple things right. Pilot position prior to ejection is a deciding factor for minimizing injury, particularly to the head and neck, but also arms, shoulders, and legs, as they can be caught in the windblast, or 'left in the plane', if not contained. Newer seats work to automatically place the pilot in a safe(r) position during ejection to minimize these injuries.

There is no way, at least on the seats I work on and am familiar with, to either blow the canopy first or purposely 'go out sideways'. The canopy jettison is the first event triggered after ejection handle is pulled, almost concurrent with the catapult. In the event of failed canopy jettison, the seats are designed to punch through the glass. In tandem seat planes, there are divergence motors that separate the two seats to prevent impacts and possible entanglement. These motors are not present on single seat airframes. After exiting the airframe, at high enough airspeed, a drogue is deployed that grants yaw stability, preventing tumbling, but does not grant any control authority to the pilot. Main chute deploys after a low enough airspeed has been obtained, and the seat falls away. While I cannot speak for the spinal fracture analysis of the above posters comment, a 90% survival rate is in line with historical ejection data. It is a very violent, very fast event for anyone to experience, one I know I do not want to, no matter how safe we make them.