Plugging a 220v charger into a 110v outlet won't kill it (however the inverse would). And all of the Chinese chargers I've used accept both 110vac and 220vac so you may not even need the step down inverter. If you're not happy with the included charger tncscooters.com has a nice 60 volt charger for $50.
http://tncscooters.com/product.php?sku=101155
Just double check the polarity of it against the charger your scooter came with to confirm that the pinout matches.
A good NEW 60v pack should still be reading at 55v total or better. And your batteries will have to be 12volt each in order to make a 60volt pack.
Check each one with a multimeter if you can get to them.
The blinking red/green is probably indicating a float charge rather than a high current charge.