It looks like the rank of their special ability will determine how high their level cap can go, and since we don't see other 'levels' in the characters' stats, I'm guessing leveling up your special abilities will result in increasing your stats.
If we compile all the level caps in MC's abilities together, putting aside whether he has level caps for 'Innate Talent' and 'Clairvoyance', his 'max level' would be 71, so the total stat points he'll earn upon reaching the max level will be near 500, which looks to be over 5 times the average person's stats if we use the parents at the end as reference.
It will certainly take more work getting to that point with his required EXP to level up increased, but that just means he'll have 3 times more EXP than average, and the gaps can get very big very quickly if MC puts in the work.