dont forget these are old brakes, steel discs and drums on some cars, so they do generate a lot of heat.
I was struggling with brake temps at Le Mans in my trials with the Gt40 as they can reach 550 degrees under hard braking
I found if you drag on the brake pedal too much leading into a corner they build up heat very rapidly. The best way i found was to give a large squeeze on the pedal (before the tyre marks on track surface) to shrug off most of the speed, release the pedal then use a series of dabs whilst downshifting and using the engine braking to slow the car right down 'before' you turn in, then coast/power through the turn in whichever gear needed. (and funny enough, thats what my FIA GT champion instructor told me once at Brands as we hurtled towards paddock hill turn in my own car at seemingly too quick a velocity to be healthy !)
Watching your brake temp in Xpd whilst braking helps here, as if you let them get too hot they will try and spit you off track when you next press the brake pedal.
Not used the alfas yet in P&G 2 so not sure why you are getting hotter rear brake temps than front? but it would suggest you need to move the bias forwards. Again, some of these old race cars had stronger front disc brakes than rears.