You've tackled this in the appropriate manner, giving the dealership from which you bought the car every chance to make it right. But that hasn't happened, so now is the time to talk to Subaru's customer service division at head office. 

The good news is that the problem has been logged as a pre-existing condition, so it will be covered by your new-car warranty even if the car is technically out of the warranty period. Also, Subaru has not ignored the problem nor refused to accept it exists, so that's a positive, too.

If for some reason, Subaru wants to abandon you and your problem (which won't happen given its approach thus far) then you could talk to the ACCC. Australian Consumer Law has some fairly rigid rules regarding products that aren't fit for purpose. This, however, would be your last resort.

It would bother me a little that the car was making a weird noise from the front suspension, and I think you've probably got a case for not wanting to drive the car until it's fixed. This could be where you tackle the customer service division for the loan of a different car until yours is fixed. I don't think that would be an unreasonable request and may hasten the problem's resolution.

The cargo cover will certainly help to restrain the luggage in the event of a crash, but it probably wouldn’t stop it altogether in a major altercation. A proper cargo barrier behind the rear seat would be more effective.

You’ve pretty much covered the field there, so it should come down to what you want from your car. Do you want comfort, safety, fuel efficiency, offroad capability, cabin space? If you are mostly driving on the highway, then a diesel SUV is probably the best bet. I would rule out a dual-cab ute because of comfort, unless you need the flexibility a ute gives you. I would rule out a hybrid, they’re not at their most efficient on the highway; they’re better suited to town use. Based on your annual mileage I wouldn’t keep the car any more than 3-4 years, that way you’ll have a decent resale value when you get out of it.