There is a picture on my activity feed.
Mathematical equivalents: Legendary: 63,550 Mythic: 76,260
I believe a score of 80,000 can be achieved at Mythic level.
I’m not as certain as you that 80,000 points is possible in Mythic Warzone Firefight as it’s much more difficult to complete the rounds quickly and much easier to die. In your game, you received 2000 / 3000 points in speed bonus and the maximum survival bonus (3000 points). Both of these sources would probably be extinguished down to a much smaller number and a deaths would be inevitable with your current strategies due to the Black Eye skull in round 2-5.