Your phone charger will work fine with this cable combination as you've probably figured out by now. Best thing to do if you have a few USB powered devices is spend a few dollars on a 'USB safety tester' like the picture below = available from Chinese suppliers on pretty much all auction sites. It will tell you the volts and amps drawn by any device plugged into it, which is usually enough to know whether its charging properly or not. Especially useful for devices that appear to be dead for one reason or another.
Like the Forma these testers usually come with USB ports that can be plugged in either way round. The Samsung is a smart charger so it will pump out a lot more current if the device you attach to it can negotiate with the charger and agree a higher current. WIth your phone it will increase both voltage and current way over the USB spec. The Forma seems to charge at about 800ma, slightly over USB spec.
