I think I just figured it out. :)
Look in ExpLevel.dat or
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Example:
16: 32,217
1. At level 16, it takes 32,217 points to get to level 17. Just take that number and divide by 256. (32,217/256 = 125.847)
2. Take the 4 byte value at the address of 0x0053AFCC. (Example: 53)
3. Divide the value taken from the memory address (#2) by the first number. (Example: 53/125.847 = 0.42352)
4. Multiply 100 to that value, and you now have the percent level.
According to the example, I have 42.352% on my level 16 character. It matches up perfectly in-game as well.
This formula works everytime. (I was almost going crazy trying to figure it out.)