IMO heat is not the cause of leakage, worn out old oil seals must be the reason. As oil is constantly in circulation in the system, it should dissipate the heat. You can install power steering oil cooler too,
Discs were available in Karachi. Contact Uzair Saleem (03329926610), he can arrange it.
Leakage can lead to stiffer steering. Alignment has nothing to do with leaking oil. Young chaps have little or no understanding of these old suspension designs. Try to find some old timer alignment guy. Try contacting Atif Riaz bhai, he may point you in right direction.
BTW why don"t you go for Mark2 original steering setup?