CAMS were actually quite helpful when I built a full cage for my Datsun last year, replying to emails fairly promptly with helpful advice and answers. And when done, I sent off my logbook application on a Monday afternoon (admittedly, complete with the $75 extra "express processing" fee), got a reply Tuesday morning to say my logbook was in the mail, and the logbook turned up in my letteerbox on Wednesday. Just as well, I was leaving for Bathurst on Wed arvo
Anyway, some stuff you need to consider:
Size and material used - Must be CDS or CDW "plain" steel (ie not an "alloyed" steel like Chrome Moly), main hoop must be 1 3/4" and 2.5mm wall thickness, other tubes can be 1 1/2" and 2.5mm wall thickness. Its going to be hard to work this out, unless you can get specifications from the manufacturer ? If you measure the size of the tubing and it isn't exactly the sizes mentioned, chances are its not correct grade.
Bending - tubes must not be crushed / ovalised by more than a certain %-age (can't remember exactly, its in Schedule J).
Mounting feet - must be a certain area and thickness (3mm thick, area varies according to weight of car). Bolt "pattern" must also meet regs in Schedule J.
Number of bends in front legs - no more than two, can't really see what yours are like.
Joints - Schedule J is very specific about what joints / how many joints are OK. Can't really see if yours would comply or not.
As mentioned, lack of backstays and lack of a diagonal in the main hoop are just two of the obvious problems with your cage.
What I did when I was designing / building my cage was read Schedule J (a few times......) and make notes on the parts that I needed to comply with.
Realistically, it could be quite difficult to get your cage complied. I'd be inclined to sell it and get one made / buy one off the shelf that comes with a certificate from manufacturer.