I don't know about that first part... In the Level 1 Pro competition, My rank is around 4600. Winning first place nets me a whoppin' 9xp, while second place is -17xp. It's not impossible to get up to 5000, it just takes a LONG time and a little bit of luck in who you are racing against... When I see that someone is slightly faster, I stop playing and get back on when other "slower" people are playing. I'm sure when you get up to the around 4800xp, the points probably go down to 1xp per race. Yes it's hard, but not impossible. Just have patience and keep at it
Close, I'm at 4824 and it's 4 rank for each first. Not sure what the deduction is for second, I spend alot of time tuning so I don't see second often.
Edit: Just accidentally bumped the nitro early and got a third. -46 rank.