The max that I was able to get the stats at is 65+. How do I get the stats even higher?
You can easily get such stats (even 300+ in all) if you have a great dev team/staff. It will take some time but it is worth it. You need to get the great staff and train them and level them up. You can hire 3 special characters as the game progresses and you win game of the year awards and sell millions of copies. Just be patient.