R163 was not shorted, in fact if it doesn't measure as shorted, you have a problem. A shorted resistor is a DARN rare thing. I don't recall seeing one in the last 50 years.
Look at the schematic. R163 is in series with the output of the channel, but it has inductor L100 in parallel. Inductor is just a coil of wire, so it has a DC resistance like wire - next to zero. If the coil is open, or more likely broken free at one end, or has a broken lead that still touches sometimes, your resistor will be left alone to measure as itself. But if the coil is intact and connected, it will be across the resistor and make the resistor appear "shorted."
Generalaly, most of the output current flows through that coil, so if it is open or not connected, then that poor R163 is now in series with your load. And the amp loses the stability the coil adds. A broken coil could have been the reason the amp failed.
Two 12,000uf caps is probably a lot cheaper than one 24,000 cap. And probably takes up less space.
For the cap betwen low and high rail ro discharge fast, there would have to be something discharging it.