Maybe I can help some atleast some credit info. made 3 extra accounts, i was curious myself and this way it was easy to avoid info getting miscalculated by friends racing against my drivers, ran all 9 races, keeping track of credit total after each race, was using 16 drivers: 1 level 28, 1 level 17, 4 level 16, 4 level 15 and 6 level 0. the info i gather from the 9 races was this;
Payouts - they do have a structured payout for the remote races. All 5 minute races pay the same. All 10 minute races pay the same. All 20 minute races pay the same.
Issue - Payouts seem to be random, you could finish 1st and receive 16th place payout. whether this is a bug or not is unknown. probably is though.
For 16 players Payout is as followed:
5 Minute Races: 1st 12,500, 2nd 8,720, 3rd 6,230, 4th 4,360, 5th 4,110, 6th 3,740, 7th 3,490, 8th 3,110, 9th 2,860, 10th 2,490, 11th 2,240, 12th 1,870, 13th 1,620, 14th 1,370, 15th 1,180, 16th 1,060
10 Minute Races: 1st 20,000, 2nd 13,980, 3rd 9,980, 4th 6,990, 5th 6,590, 6th 5,990, 7th 5,590, 8th 4,990, 9th 4,590, 10th 3,990, 11th 3,590, 12th 2,990, 13th 2,600, 14th 2,200, 15th 1,900, 16th 1,700
20 Minute Races: 1st 35,000, 2nd 24,490, 3rd 17,490, 4th 12,250, 5th 11,550, 6th 10,500, 7th 9,800, 8th 8,750, 9th 8,050, 10th 7,000, 11th 6,300, 12th 5,250, 13th 4,550, 14th 3,850, 15th 3,320, 16th 2,970
remember, this is just the order of payout, doesn't mean if you finish 1st you'll get 1st pay, also it didn't seem like there was a favor towards lower levels, highest paid after the 9 races was a level 0 (earning 94,400), after that it was level 16 (earning 93,970), level 28 (earning 88,200), another level 16 (earning 64,030), then a level 15 (earning 62,410), that was my top 5, my guess is just go with the flow and hope you get lucky enough, maybe one day they'll fix the pay so it rewards correctly.
sorry this post is so long if somebody wants to repost this they can, just wanted to help after finding the amount of credits that can be won for the 9 races for a 16 player race, thats all i got for now