P&W performed a thermal stress analysis, a thermal creep analysis and several other types of analyses concerning deformation and elongation of the combustor can. Based on these analyses it was determined that the combustor can had a reliability of 1 10e9 . Obviously from what you have indicated there were several other explosions of the combustor can and therefore the combustor can did not meet the predicted reliability of 1 10e9. My question is what did the FAA do regarding the inability to meet the predicted level since this is what Boeing relied on in the design of the under wing surface.
There was no analysis performed, nor requested/required, to show anything would meet a E-9 reliability. Its ludicrous to expect a structural part to show such a reliability in a hot section of an engine.
The FAA does not pretend that such a reliability can be met and Boeing must presume under FAR 25.903D1 that any part of the engine may be ejected from the engine towards their aircraft.
If this is the case the nacelle had to be torn apart for the combustor can to fall harmlessly onto the runway. Also with an uncontained explosion there had to be a fire. So while the remnants of the combustor can were laying on the runway what was happening to the aircraft?
Well you've got the idea and yes the nacelle is presumed to be torn apart along with its fire fighting capability and yes the combustion fire will be expose for as long as the thottle is left in the on position. In spite of this numerous similar explosions and short term fires have occured without the unique consequences of the Manchester accident.
In short there is no requirement to perform a system safety analysis on a structural element and in the case of engine elements the FARs require the presumption that any such element will eventually fail and that the aircraft design need take some degree (not total) of mitigation.