Hydrogen peroxide definitely kills everything it comes into contact with, good or bad. I hadn't heard of diluting it down, although the concept seems to make sense. As an alternative, I tend to carry a couple of providone-iodine wipes add to water; the wipes come as a 10% PI solution, which is again too strong, but you can simply add the wipe to a liter bottle of water and steep it like tea. When the water gets to the color of a strong tea or a Newcastle, it's at a 1% solution and is suitable for cleaning wounds.

Probably the most important thing to realize, though, is that the sterility of the water used to clean wounds doesn't matter; there has been at least one study that shows that tap water is just as effective as sterile saline. What matters more is flushing the wound under pressure (such as through a syringe, or a ziploc baggie with a hole pricked in the corner) to move the bacteria out of the way. I pack the PI wipes for situations where there might not be a lot of water available to me, but my first choice is always about a liter of drinking-quality water.