The watchdog timer postscaler & on/off options are configuration options. These are set at
program time.

PBP allows you to DEFINE pretty much anything without throwing an error, but that doesn't
mean your defines are doing anything.

If you're using the older version Microchip USB boot-loader firmware, these are set in the C
code.

Code:
#pragma config WDT      = OFF
#pragma config WDTPS    = 32768
You can open the loader .HEX file with your programmer, change WDTPS from 32768 to 128
then save the .HEX file & re-program your 4550 with the modified loader firmware. Then you
will have a postscaler of 128. I would leave WDT=OFF, and use the software enable option
WDTCON.0=1.

You'll also want to use DEFINE OSC 48 so PBP will use the correct timing. Without defining
the osc speed PBP defaults to 4MHz.