Cave Diver once bubbled...
Light cannister is worn on the right waist belt. Preferred to have light head in right hand which prevents the cord from draping across your body and inhibiting access to your hoses, etc. There may be some instances where you need your right hand, and the light will be switched to the left temporarily.
I dive the 7' hose with my single tanks. In lieu of a light cannister, you can use a knife sheath or some sort of pocket to secure the hose. Tucking it into the waist strap also works, but not near as effective IMO.
A breakaway connector is an o-ring or something similar that will "snap" when enough stress is placed on it. Use it on essential items that have a secondary method of securing it.
Ex. Use an o-ring to connect the bolt snap to an SPG. If your spg hangs on something, the o-ring will break rather than causing you to get hung. However since your SPG is attached to a HP hose, you cant "lose" it in the event that your o-ring breaks.
By contrast, your backup light bolt snaps should be secured by cave line instead. Much sturdier than an o-ring, and not likely to get broken accidently. They are however, still cutable in the event of an emergency.