A:
Sure. If you can use a your USB port on a PC or Laptop, the voltage on the wall charger shouldn't 'blow up' the Bose battery or the like. If you can find a 4.5 or lower voltage one at some point if you want to play it more safe, so be it, but it's just a lithium ion battery.
If anything, you may find it charges much faster. Just check how warm the battery gets as it charges and the length of time it takes- if it gets unusually hot and charges in a ridiculously fast time, then maybe the wall charger has too much 'push', but if it was my rig, I'd let 'er fly..
I couldn't find a spec on the 'optional' wall charger, if there even is one from Bose as they specifically point users to the USB ports on PC's..