Assigning workload to available users

Hello,

I'm trying to work on creating a spreadsheet that will automatically assign cases to available users evenly (Assigned user goes in column A)

For the attached example I have 217 cases and 13 available users. I need items assigned out as a priority as follows:


Cases with "Late Stage" in column M should be assigned to the case owner if they are listed as an available user.
Cases with amounts over $500 should be assigned to the case owner if they are listed as an available user.
(I'd like to be able to add one more priority at later time-- so say if column L says "Placeholder") should be assigned to the case owner if they are listed as an available user.

No available user should have more than another user EXCEPT all cases with the same customer need to be assigned to the same user. This is where I'm having trouble. Right now in the example User 9 would get assigned the large group of cases for "Jim Bob Johnson 38" if he was an available user but if he isn't the cases get divided out regardless of the fact they're for the same customer.

The macro also doesn't assign out the whole list as it stops with some remaining. I would be very appreciative if someone could help me tweak it to fit these specifications!