The aftermarket service manuals are ok. But if you want to be exact and be able to fix diagnose the exact not generalized repair download the factory version.
There are items that are " hot " have power available but are activated by a switched ground. Versus a switched power.
If you believe your drain is through that 50 amp feed fuse you could just unplug one item at time to find the parasite drain item. Then examine why , or how it's causing the drain.
For the more complex diagnosis, and if you plan on long term ownership, you can't beat using the OE factory service manual.
Good luck.