The zener in the 2917 is for supply voltage regulation, it has nothing to do with the maximum input voltage.
Transformer resistance is mostly irrelevent, it is the winding inductance that determines the load it presents. That is why you need a reasonably high voltage transformer, so that it still lakes a reasonable magnetising current at low frequencies.
There is nothing very demanding about the transformer at all, anything in the region of 120v to 3v up to 20v should do. Even an ac output wall wart should be adequate.
It is possible to capacitively couple the 2917 to the diode bridge and it is also possible to use an opto isolator but in either case you really need to know what you are doing. The 2917 is a really nice device but its input circuit is not the easiest thing in the world to drive from messy waveforms associated with rectifiers, it will easily respond to harmonics in the waveform and give wrong answers. The transformer is far easier and even then you may need a bit of filter under certain conditions.
The input of the 2917 must cross zero, if you use an opto isolator you will need a capacitive coupling to the input.
Flux