Hi Hans. My apologies for the delayed response as I must have missed notification from your first reply. 
In the example I showed above in the second photo, you'll notice that the tablet is installed above where the Wink Relay used to be in the first photo. And while it's not completely shown in the photo, the switch below it was converted back to a normal physical on/off switch. So I wasn't using the Wink Relay at all any more, nor pulling power from it or the switch.
In my particular case, I had some cabinetry on the other side of the wall which had a power outlet in it. I simply drilled a hole through the wall and into the cabinetry and then ran the USB power cable through the wall.
Another popular solution is to install a Recessed Electrical Outlet behind the tablet (and typically connect power to a switch nearby) - the Arlington Recessed box is popular among the tablet-mounted crowd.
All that being said, you can scavenge power from the Wink Relay wall unit. Some people specifically buy broken Wink Relays just so they can use the in-wall component as a power source for their tablets. I don't recall which pin is which, but from what I remember one is power, one is ground, one is for the top relay, and one is for the bottom relay.
Regarding the Wink Relay, I would note that the STWinkRelay app doesn't remove the original Wink Relay APK in any way. It simply disables it. I don't understand why you wouldn't be able to do a hard reset?
From the Wink Relay wiki on Wink@Home:
- While holding top right switch (physical button) on Relay, press soft reset button underneath faceplate
- Continue holding top right button until “System recovery” screen appears
- Press bottom switch twice, or until “wipe data/factory reset..” is highlighted
- Press top switch once to select “wipe data/factory reset..” option
- Screen will display message - “Confirm wipe of all user data? THIS CAN NOT BE UNDONE”
- Using bottom switch, navigate down until “Yes - - delete all user data” is selected
- “Wiping data… Formatting /data…” screen will appear, followed by original “System recovery” screen
- Press top switch to select “Reboot system now” option. "ERROR" may appear on screen, this is normal.
- Relay will reboot, and should eventually load main Relay home screen. If home screen does not load, Relay may require one more soft-reset (press button under faceplate).
- Relay should now show newest firmware. If this is not the case, simply perform update again