Yes, the success metrics are measured on the training set.

I just ran a measurement with a separately generated testing set consisting of 52k characters which yielded a success rate of 98.53% on letters a-z. This turns out to be almost exactly the same as the rate presented on the repo page (98.52%). Will upload the result for your perusal as soon as possible.

You will have to browse the synaptic neural network library [1] for an answer to your second question.

[1]: https://github.com/cazala/synaptic

EDIT: A separate testing set is now generated in addition to the training set. I updated the success rates of the examples in the readme accordingly.