@jujubeam BTW, no matter what, there could never be a 'crazy $$$ bill afterwards'. Since Public Mobile is prepaid, there are never ay charges after the fact.
As mentioned, you can tether for DATA (from your wife's phone). However, your phone number will not be usable (incoming or outgoing calls). Texts (SMS) will also not work.
There is no roaming in italy available. You do not need to disable/change anything on your phone. There will be no roaming charges since this is a prepaid service.
When you get the prompt for the security code, there should be an option to send it via email. It is not shown the first time, but after that, it should show up as an option.