Altering button title it becomes inactive
Your mistake is this line:

$form['actions']['submit'] = array(


It replaces original button with your own brand new array. Nothing in it, except what you put there. Original node form have submit function connected directly to a button, but you destroyed that with this line. 

Instead of deleting original array and creating new one, consider simply altering values you need altered, like:

$form['actions']['submit']['#value'] = t('Activate');