You don't need to modify core files for this. There are 2 things you need to do. First, you can change the name of the menu item in the language settings. See here for the simplest method. For example you'd need to add this in qa-lang-misc.php:
'nav_user_wall' => 'Pin',
Second, use the $QA_CONST_PATH_MAP option in qa-config.php. For example:
$QA_CONST_PATH_MAP = array(
'wall' => 'pin',
Edit: sorry just realized that won't work. You're asking for the wall page for every user I think... so scott/wall, esqeudero/wall etc? It won't work with dynamic URLs. In which case yes the way you've done is currently the only method.
The navigation link you're missing is in the qa_user_sub_navigation function which is in qa-include/app/format.php. In the second bit of code you changed, you only changed the 'selected' menu item (i.e. the one that appears blue). In that function, on the 'wall' key change the URL to have /pin at the end instead of /wall.
You'll need to do similar things for the other user pages. For the questions?sort=X URLs, look for case 'hot': and so on in qa-include/pages/questions.php. There are 2 occurrences of each.