You can check ebay for a 'digitizer' if that is the problem (could also be a failing connection)

https://www.ebay.nl/itm/Touchscreen-...AAAOSwcvdXO1zv

If you have access to your N900 and keyboard is working you should be able to copy/paste everything you need to sd card.

This might be helpful to work with your device without touchscreen.

http://wiki.maemo.org/N900_Shortcuts...eral_shortcuts
https://wiki.maemo.org/Terminal

If you like to backup everything and copy it over to your spare N900 I suggest to install BackupMenu http://talk.maemo.org/showthread.php?t=63975

I don't think touch screen is mandatory for any of these actions.