All of these can be done by editing the plugin manually and should not be very difficult given that the plugin is lightweight and compact.
Using your editor, navigate to: include\class-side-bar-login-widget.php.
This workaround is not CLEAN, but it will allow you to revert your changes should you need to without hassle.
Change:
. 'label_username' => __( 'Username', 'sidebar_login' ),
'label_password' => __( 'Password', 'sidebar_login' ),
'label_remember' => __( 'Remember Me', 'sidebar_login' ),
'label_log_in' => __( 'Login →', 'sidebar_login' ),
'remember' => true,
'value_remember' => true
) );
To
. 'label_username' => __( 'USERNAME_TRANSLATOIN', 'sidebar_login' ),
'label_password' => __( 'PASSWORD TRANSLATION', 'sidebar_login' ),
'label_remember' => __( '', 'sidebar_login' ),
'label_log_in' => __( 'Login →', 'sidebar_login' ),
'remember' => false,
'value_remember' => false
) );
As you can see, you will change the ‘Username’ and ‘Password’ label as well as hiding the ‘Remember Me’. You can go as far as actually removing the label if you wish, but that is slightly more tricky.