I thought Allah was omnipotent, meaning all powerful. I thought Allah could do anything. If this is true why does Allah need the help of human beings to be his Khalifah "to ensure the Physical Creation unfolds rightly according to His Will"? I think this question is very important so can you please answer it?
You are right; Allah is omnipotent, all powerful. There is nothing Allah cannot do; therefore, Allah needs no help from anyone. The reason that Allah has created human beings to be His Khalifah (helper) is that for the completion of our spiritual advancement we need to be Allah's Khalifah. So rather than Allah creating us to be His Khalifah because He needs our help, Allah through His unparalleled Mercy has granted us the opportunity to be His Khalifah so that by successfully fulfilling the responsibilities of that most honoured role we may fulfill our spiritual destiny.