[christianw.]

For using just one button you'll have to take care how the interrupts/timers are served. You simply can't have i.e. long + vvlong on one button as these are not edge controlled. The "long" will always superseed the "vvlong" here. So better combine these with the "release" button interrupts.

Have you tried connecting D+/D- with a 100R resistor and powering it from VUSB + GND? This is the simplest configuration for a "dedicated charger".