The primary cause of your tyre failure looks like excessive wear caused by incorrect alignment; the rear wheels should toe in; it looks like yours must be toeing out. Possible excessive toe-out would also account for your tyres looking a bit flat when they're not, although under-inflation may have been a contributory factor. Budget tyres (Kormoran?) wouldn't help the situation either.
The 156 rear suspension is not particularly robust; "kerbing" the wheels often bends the long bolt that passes through the bottom of the strut and the two transverse arms, affecting the alignment. You need to take the car to someone who knows what they're looking at.