Final credit score of 18640. Best I can do by hand. The RNG is very much like a gambling RNG and appears to favor you less the more you earn. Actually maxing out the credit counter in a reasonable time frame will probably need a high level of Lua scripting and a much better understanding of the RNG. Disassembly of the game code may be required in the process.
I should note that a combo of landing on a BAR or 7 and getting a matching BAR or 7 from the brick Fortran hits will double the credits earned for the round.