The PS will definitely take care of the hum. Those wall warts are notoriously poorly regulated even if a half amp was adequate, which it is not for two radios. I'll send you a supply.
The WiFi router IS the source of the digital hash. It is most likely getting into the radios via the audio and power cables, not the feed line, so what you need to do is snap some ferrites around those cables (the donut things you see on VGA cables and such. You can get them at Radio Crap. You should wrap as many turns through the donuts as you can, and as close to the radio as you can. If that fails, you can install the radios in a metal enclosure with feed-throughs, but I'd try the beads first.
As to the jackhammer, that's one (or more) of the channels on the scanning radio generating an oscillator frequency that is mixing with something else and generating a mirror in the other radio. Depending upon the radio and circumstances it may be impossible to eliminate, or as simple as adding a reject stub here or there. I have even had situations where radios had such cross-talk when on two different antennas... signals going up the feed line, jumping between the antennas and back down the other side. In your case, both radios probably have the standard IF (Intermediate Frequency... the difference between mixer oscillator frequency and received frequency) of 10.7 mHz, and it just so happens that the 121.5 channel on one radio is 10.8 mHz away from the 132.3 on the other which means that depending upon whether by design they mix "up" or "down", the 121.5 radio could be providing interference on 132.2, or the 132.3 radio could be interfering at 121.6 100kHz is not much for bleed-box scanners with high gain front ends. Now, if that cross-talk is via the audio and power cables, the donuts will fix that, too, and the fact that the addition of the amplifier cleaned it up tells me it brought the noise level up from the desired source (the antenna) and swamped it out... but it is still in there.
One thing you could definitely do that costs nothing and can only help, would be to tee-in a half-wave open (or 1/4 wave shorted) 133.15 coax stub on the 132/134 radio, which will act as a band pass filter. The other radio has 121.5 and 135.8, so there's not much you can do about that one. But first you need to de-couple the power and audio lines, then we'll see where we're at.