Definitely all fixable, but I'd take some time to really think through the user journey here. It's a completely new paradigm so it's going to be hard to grok.
The 'oauth on another device' issue is partially fixed now - if there is another active device/browser that can send authUrl then you'll see login screen first, and if you login it will proceed to asking for confirmation etc. The unresolved case of 'there are no active devices that can send authUrl' stays, will be fixing it differently.