I doubt it'll overload the PA head's mic amp if you substitute 3k3
for the 10k above.

I'm somewhat confused here... if I use 10K and 100R then I am going to
get 10mV (max) output for a 1V max input. If I use 3K3 then the output
will be 29mV. In both cases, surely this will overdrive the PA mic
input, which is expecting just 3.7mV max ???