When you bought the car, a special 'selected' used car, did you look underneath it to see if this level of rust was there already? Surely CC wouldn't sell a car with this level of rust, especially a 'selected' one?
If not, how have you used the car to get it in this state in a such a short time? Have you run it all year road with no rust protection (Waxoil/ACF50 etc), put it away wet after salty runs? I guess you might have learnt the hard way that 7 are not at all like a modern car in this aspect, and need regular (annual?) check over and if necessary treatment to keep on top of rust on the space frame/ suspension. A good clean underneath on axle stands/ ramps will allow you to see where the rust is more easily allowing remedial treatment. A flapper wheel on a drill or dremel, clean & paint the problem areas then a top coat with Waxoil or similar would be too hard.