Okay, so, funny story... Your math is correct, and it's definitely the right way to go about calculating the steps per degree, and your number should be the one that's used in the firmware.
But, when I was testing it the first time, I had done a math error in some of my calculations. I did the gear ratio backwards, and ended up multiplying the result by ten to get a number that was reasonably correct. It worked perfectly for all my testing, and ended up in the final product as seen in the code. However, when I did a check-up on all the numbers to comment everything for the V1 release, I found the error and fixed it. Upon doing some testing with the new number, it was just slightly off, so I changed it back to the one that I knew worked and left it there.
Definitely give your values a try, but if they lead to discontinuities, try the 57 degrees again. Sorry I can't give you a better answer, but I hope that explains it!