One last thing we can do. It is a bit odd that your version of MySQL is complaining on this when I'm running the same on my test box. Let's just alter the importer directly.
Line 505 of threads_import.php looks like this:
// INSERT into USER_PROFILE
Right before that, add this:
if (!$user_data['U_FloodControl']) {
$user_data['U_FloodControl'] = '0';
}
After that is changed you can try the import again.