Does someone have a reference to an "official" formula? (Or did someone decompile the code?)
The survival and last survivor bonus are correct for 1v1 but for melee/team the folling is a more complete description:
50 points for each survivor when an opponent dies (by coming first in a 10 bot melee round you will have aquired 450 points - because 9 bots died before you)
Last Survivor bonus = 10 * number of opponents at the start of the round. For a 10 bot melee the bonus = 90, 1v1 the bonus is 10.
In a 10 bot melee battle survival points are distributed thus: 10th = 0 9th = 50 8th = 100 . . . 3rd = 350 2nd = 400 1st = 450 (+ 90 last survivor)
A standalone class for keeping score in 1 on 1 is available here: CalculatingScore