making form input text safe

I am using the following code to input some text into the logged in users meta
(this code is in the page template)
I am not sure exactly how to make this safe, I have used wp_filter_kses so far. But is this the best method? I am not using database tables, just inputing into the user meta and post meta.
I want to strip all tags and all characters apart from the alphabet and spaces. And I want to make sure I am not causing any vulnerabilities.

<form id="formid" action="" method="POST">
  <input type="text" name="inputname" value="" />
    Name: <input type="text" name="fullname" maxlength="75" /><br />
  Email: <input type="text" name="email" maxlength="35" /><br />
  <input type="submit" name="submit" value="submit" />
</form>

<?php 

    $inputname = $_POST['inputname'];
     $fullname = $_POST['fullname'];
      $email = $_POST['email'];
   $inputname =  wp_filter_kses( $inputname );
   $fullname =   wp_filter_kses( $fullname );
    $email =    wp_filter_kses( $email );

    print_r ($inputname);
    echo '<BR/>';
    print_r ($fullname);
    echo '<BR/>';
    print_r ($email);
    echo '<BR/>';

////then some code to input the text into the logged in  users meta

?>