I don't know the exact number, but there are a couple of variables something like player_level_exp_current and player_level_exp_total. You'll find them if you search for "exp" anyway. Those are the x and y of the "x / y" progress to next level-up. The total increases with each level.
2000 for lvl 2.
4000 for lvl 4.
5000 for lvl 5.
6000 for lvl 6.
7000 for lvl 7.
117000 for lvl 117. (Yes, I checked.)
Total xp you need for lvl 20 is thus (1+2+3+...+19+20)x1000 = 210,000.
Edit that variable to be 211,111, download the edited save, cut from downloads, paste into saves, load in game, go beat something to earn xp, click the level-up button and spend your points.
You still need to follow the quests to unlock melee combat and get armour and a sword and yada yada yada, but at least you'll be level 20.