I've probably spent at least 40 hours just reading through the code base and trying to get familiar with how everything is put together.

I've never been in this position before, having to do this solo. Usually I have the people who wrote the code to turn to with questions. Or at least a team of fellow reversers to give things a second pair of eyes.

I've spent so long quickly going through code to find the security problems, now I'm having to re-learn how to grok everything at once instead of just the security critical code paths.

It's a good challenge. Sharpen those skills