Solved

Problems during the race

That's difficult to answer, but one thing to remember is that the starting car is not improving with level, also research gets slightly weaker with level. So while the HQ generates at level 15 2 points less compared to a level 17 it's not impossible to make it up with fine tuned research, or if that's done better even pulling ahead in a few areas.
Also with drivers the really important stats are Talent and Stamina, a few points in Driving Ability are not making that much of a difference and Mental are really weak skills. At those levels things like fuel management, push level (there's more to it than just keeping the temperature in the green and I'm sure there're manager out there that are quite a bit better adjusting it during a lap than me for example) and playing out strategy to work with the traffic are more important. I'm not trying to insist you're doing a bad job, just that's it entirely possible to overcome more than that kind of level difference.