The scoring system is broken unfortunately. As far as I understand it the only two factors involved in the final score are Founding Fathers and the amount of land you control - so your OCC win is heavily penalised (but congratulations anyway).
In the original game there were many more factors involved - Number of Citizens, Number of Founding Fathers, Final Gold amount, Rebel Sentiment at Independence, Early Victory bonus, Liberty Bells produced after Independence and the number of Indian Villages destroyed (that was a negative). Then there was a multiplier for achieving Independence and another for the difficulty level. I have no idea why this comprehensive approach was dropped this time around.