Since one of the original questions has not been answered, I'll do so. The BL stands for Back Light meaning that the lcd pannel is backlit. To save the hassle of having to connect the voltmeter leads all the time, I soldered them ahead of the powerpole connector on the T35 side, so they are always connected.
If you regularly discharge at 30A, you should check the charging side power pole connectors periodically to make sure they have a snug connection. If they are loose, there will be a lot of heat generated and it will melt the powerpole connectors, possibly fusing them together. How do I know this?
Also, since it only take 500ma (1/2 of an amp) to permanently stop your heart, be careful when dealing with high current like this. I suggest the number 1 rule of an electronics tech. Keep one hand behind your back so you don't create a circuit across your chest.