So far so good...

Let me get that right. You did 'cp -R yourfile.sh /bin/sh' ? That was not the wisest thing in the universe: /bin/sh is a file, not a directory. If you've really done that, you have overwritten your command-line interpreter. No wonder your phone now does not boot. That interpreter also runs all the scripts including start ones.

On a Maemo system /bin/sh is a symlink to busybox so there might be a chance to fix it but I would not have a first idea how. You are in a Catch 22 situation: you need sh to fix sh. Unless someone comes up with a better idea, you may need to reflash your phone. Combined (also called Fiasco) only, so you can rescue your data. But you will still need to reinstall all your updates and extra apps.

BTW, instead of copying your script to a system directory, all you needed to do was specifying the full path when you were running it. If you were in the same directory, './yourfile.sh' would have done it.