Quick reply...

It looks like a hardware problem, if the LCD screen can display and touchscreen doesn't work. Either go to Nokia support or be prepared to take n900 apart to find the reason of the problem.

"Enter lock code" doesn't accept numbers from keyboard. So I assume that keypad isn't broken.

In case it is software problem, remove battery and put it inside again.

The device doesn't seem to have any Internet or cellular connection, so you cannot control it with SSH or SMS commands.