- Alright. In case you would lose your connection between debug adapter and the device, repowering of the former could help.
- Ok! I do not think there will be one, but please check. Regarding the OpenOCD, the latest one is v0.11, which could work better.
- You should be able to get away with just SWCLK and SWDIO, without the 5V and GND (though the latter is recommended).
- Alright. Please remember to disconnect the debug adapter when connecting to the USB, otherwise something bad can happen, depending on the debug adapter internal connections.
Happy to help! I just happen to have this fresh in the memory. I can do so only to some extent though, as this is not officially supported. And I am running out of the ideas too.