Brake questions

[bw4sale]

Ok, my pedal travels a lot before there's resistance. When it hits, it's very hard. I pulled my cap off the MC and the front half was completely full, back was almost empty. I seem to remember it being this way before when I first got the truck about 2 years ago. I think I filled the back then and it hasn't really been driven since then. Do I have a leaky cylinder or something? I pulled the back drums just to inspect a little. The drums look good. The pads looked pretty new. One pad was more worn than the other on my passenger side. What does that mean? How do I inspect the wheel cylinders and the other inner parts? Overall it looked better than I thought it would. Thanks.