Backlight troubles - help me identify the failed part?

My Macbook's backlight is broken. Occasionally it can be induced to turn on, but the laptop is effectively unusable without an external monitor.

I'm hoping to identify what part is likely at fault.

Here are all the observations I think might be relevant:

• "Backlight is broken." Under the right lighting, I can faintly discern the proper display on the screen. (Screen looks black to a casual glance though.)

• Works like a charm connected to an external monitor. No issues.

• The "Apple light" on the back of the upper case fails in tandem with the backlight. When I briefly get the backlight on again, the Apple light comes on too.

• The screen is cracked. I'm not sure if this is relevant to the issue, because the crack was there for at least a couple months of use before any backlight issues cropped up. I've attached a picture - you can see the black areas, mainly localized to the crack in the corner but also along screen edges. I'm happy to have the backlight up and running again with a cracked screen - actually, I don't really have the money for a new LCD panel.

• Screen position affects the issue. When I get the backlight working again for brief periods, it will go off again if the screen attitude is changed to a different position (or perhaps just if it's moved at all).

• Brightness affects the issue. When I get the backlight working again briefly, it's at minimum brightness notches (after going to 0 brightness). Going up too far causes the backlight to flick right off.

• PRAM affects the issue. Zapping PRAM on boot can sometimes bring the backlight back (briefly!) when other methods (changing screen attitude & turning brightness all the way off, then up one notch). Often, even when I CAN'T seem to get backlight on at all, zapping PRAM twice will get the backlight to flash on for about two seconds during boot.

• I think that prolonged periods of no use of the laptop (several days) raise the likelihood of getting the backlight working again (briefly!) afterwards. NOT sure about this one though.

• When the backlight fails (i.e. after the brief periods when I can get it on again), it sometimes immediately goes out, but sometimes flickers for a second or two.

• There was a "slow decline" before I got to this stage, where the screen is basically unusable (I can't get the backlight on for long enough or stably enough to actually use). For about a week after the backlight first failed, turning brightness down all the way then up one notch, coupled with some screen moving, could often get it going for a while (~15 min?). And zapping PRAM could get it going for a few hours. It also wouldn't turn back off at the slightest touch, like now.

Help me, iFixit denizens, you're my only hope!