I tried connecting a logic analyser to the I2C bus on the Raspberry Pi so I could see what was happening with owfs when the Raspberry Pi boots and the values it writes to the DS2482-100 does not appear to change when adding "activepullup" to /etc/owfs.conf so I don't think that functionality has been enabled in owfs.
Without the active pullup option enabled I am measuring 4.6V at around 3.5mA on the OW pin on my 1 wire Pi so there should be enough power there to run a sensor in parasitic mode. The DS2482-100 must have a pull-up resisitor or some other circuitry that provides some power even when active pullup is disabled.
Can you check your owfs.conf to make sure the line "server: FAKE = DS18S20,DS2405" is commented out with a #. If this line is still active then that could explain why the sensor is stuck on 85 degrees as it would be reading from a fake sensor instead of the real one.
Would it be possible to replace the DS18S20 on your weather station with the DS18F20 powered version?