Alright, i'll say what I know:
-The GBUs can be locked onto the crosshair by the gunner, if they press T, it'll lock onto the crosshair, dropping the bomb will result in it hitting there. Note that all lockon weaponry can be used more effectively from the gunner position. This includes AAMs, ARMs, AGMs, and guided bombs such as the GBU. It also recommended the pilot only has gunpods and missiles, if anything, as the gunner can focus and more accurately drop bombs. I can't seem to reliably lock things from the pilot seat.
-The bomb computer, as well as being an indicator in the bombsight, is also a physical instrument on the main control panel. It is more accurate at subsonic speeds, but when going mach i'd recommend entering a shallow dive to give yourself a longer window to drop. Tumbling bombs, like napalm, cannot be accurately predicted, and as such do not have a prediction on this sight. The most accurate method of dropping napalm is a shallow dive at high speeds, then dropping when your crosshair is on the target and pulling up immediately.
To set a target for the bomb computer, you place a Shift+LMB marker on the map where you want your bomb(s) to hit, and align yourself to fly over it.
-The "TARGET" section reads a degrees and a distance. The degrees is your left and right deviation. If it is -1, you are one degree off the to left of your target, if it's 1, you are one degree off to the right. This should be on zero. The distance is how far you are from the marker you set.
-Below that, is the Impact. This will tell you, if you were to drop your bomb right now, how far it would go before hitting the ground. This can be useful if your target marker is slightly ahead/behind.
-Below the impact, is almost a kind of drop indicator. It will read "Short" if your bombs will undershoot the target, "Long" if your bombs will overshoot, and "On Target" when your bombs will land on the target..
-To the right of all this, is the release indicator. It will decrease as you approach your bomb drop point, it goes up to 4km, and will decrease as you approach the drop point. when it reaches 0, your computer will read "ON TARGET" and that will be the most accurate drop.
This is what i've learnt so far, I hope it's helpful!