Yeah... maybe not exceeding the level cap would be a good place to start for future attempts at save editing. It's planned to max out at 10 and is currently 6 so feeding the game a number that's eight times the largest that it's ever going to expect is just asking for problems. The best that can be said is that you're not in Floofthulhu territory...
As mentioned, once you mod your save you're totally on your own for any bug reports beyond typos because it's not worth the devs' time to try and sort out whether there's actually a problem with the game or it's just something you did by causing the game to divide by zero.