I managed to reconnect the Mac Host, and run a debug as a iPhone4s. I then switched the target device to iPad Retina and attempted to start a new session.
I received a warning and an error:
Warning: 'The executable name (FormsTemplateiOS) and the app name (TeachersiOS.app) are different, this may prevent crash logs from getting symbolicated properly.
Error: Failed to start application on the target simulator.
I found FormsTemplateiOS in the Teachers.iOS properties as the assembly name and modified that. I don't understand why your project template uses that rather than ohhh the project name but ok.
To fix the "error" I did a clean then Debug->Start new instance and the simulator switched to the iPad simulator.
Reconnecting the Mac Host consisted of the following steps:
1) Unpair the Mac Build Host
2) Shut down Visual studio
3) Restart Visual studio
4) Wait patiently for the warning message about no host, double click the warning message and enter the verification code.( a working reconnect/recover option in the toolbar would be really really really really really nice)
5) Hope that the VS addin doesn't convince itself that another instance of VS has connected to the host......