Nope, all are essential products.
Yes of course, most people use it that way. I have shared pros and cons of both products but its hard to say to which one better. Also I haven't compared all the spray waxes sidebyside.
Since you have already bought APC and dressers, Sonax Xtreme Cockpit cleaner matt finish and Sonax Xtreme Wheel Cleaner will only be additional products.
Sonax Xtreme Glass Clear Nano Pro, is a cleaner and water repellent in one. Not sure how good it is. Have to research.
I think its a polished aluminium. Brake dust is mostly caused by disc brakes then drum brakes and it can corrode the aluminium. Also it makes wheels look unattractive. I don't problem with cleaning Brake dust, it goes away easily, even with car shampoo.