As for bone "setting," don't do it. Immobilizing, please do! I've never seen anyone screaming in agony from a broken bone, and I've splinted A LOT. Moans, cursing, "owowow...." for a few seconds. There are a few fractures I hear that hurt like crazy: femur, pelvis, though the only femur I ever saw the kid was surprisingly calm. These folks might scream. The main reason to splint, though, is to keep the bone from moving. Why? Every time that bone moves, the jagged edges are ripping muscle, tendons, the periosteum (it's kind of a skin-like membrane that coats the bone, and full of pain fibers). Also, those edges can cut blood vessels. Did you know you can lose over 2 liters of blood in a femur fracture, and over a liter if you break your forearm? So, tell them to tough it out for about 2 minutes.

With wound healing, recent studies HAVE shown peroxide to kill fibroblasts, which are responsible for repairing the wound. Not sure how much it'll slow healing, but just a heads-up.

As for my top 5, seen over the past 10 years:
1) Black pepper in a wound just makes it dirty, not stops bleeding.
2) Don't ice burns. Cold water, compress, NO ice or butter!
3) People putting a tourniquet on a bleeding finger. Do NOT use below the elbow or knee!
4) Hyper-panic parents. Just plain annoying. If you kid was that bad off, why did you drive 10 miles to the hospital instead of calling 911? Or why did you wait a week before coming to the ER (my personal pet peeve)?
5) Yelling, "Damn it (fill in name), don't die on me!" while simultaneously slamming your fist into their chest is MUCH more effective than CPR, medications, or a defibrillator.