1. Can't comment without knowing the details, but it can be complicated to get the skills assessments.
2. Getting married would have the same effect, as far as the visa is concerned, as registering the relationship.Lodging an application that can't be granted and relying on the AAT is not a strategy I'd propose. You must make sure you meet the relationship requirements at time of application.
3. Getting a second WHV will solve all your problems.
4. Your main issue is that you are in a relationship with an Australian, so it will be difficult to argue that you are a Genuine Temporary Entrant. It might be worth looking into bridging courses for nurses though, as that could possibly be a legitimate pathway.
2. Getting married would have the same effect, as far as the visa is concerned, as registering the relationship.Lodging an application that can't be granted and relying on the AAT is not a strategy I'd propose. You must make sure you meet the relationship requirements at time of application.
3. Getting a second WHV will solve all your problems.
4. Your main issue is that you are in a relationship with an Australian, so it will be difficult to argue that you are a Genuine Temporary Entrant. It might be worth looking into bridging courses for nurses though, as that could possibly be a legitimate pathway.