What do you mean screen crackling issue? Do you mean when pressing on a certain part of the screen it clicks a bit? Wow, that is not a big deal. There is probably just some dirt causung it to stick. You can clean it with a sheet of paper, or even just ignore it. I just had to check right now if mine does it.

And your usb most likely was fine.

There was nothing wrong with your n900. You should of just kept it.