One does not need the distance to do phrf, you would need the TOT factor, loking up a 165 it is 3416, 168 3401, so will do those two boats
165 6.0422 hrs x 3416 = 20640 secs
168 6.676 x 3401 = 22705
This is with a TOT factor for winds in the 0-15 range, There is another factor for 15-30 and 30 and above, or some such thing in the formula. the 168 boat a final corrected time of 6.3 hrs, you at 5.733 hrs. AGAIN, this is for the light wind. Being as you had heavy wind, the TOT factor could very well be what the correct time is.
here is the formula for the factors I uses
FORMULA = 650/(520 + T/D RATING) X 3600
Non-Flying Sail Adjustments and the Time on Time Method | Pacific Handicap Racing Fleet
Now I have to remember if the 650 or 520 is a moving figure base on wind strength. I'm recalling the 650 would go to 550 and 450 for the mid and high wind range in TOT scoring. Which with the 450 figure, your times could be correct.
Example of one I figured a few years back. my final time was 3hrs 15 min. The above TOT put me at 3 hrs, mid wind tot 2:45, high wind 2:30, TOD about 2:25 for correct time in hrs and min. from memory