Cannot use formula and have a summary field using this relationship.

I am not sure I am following #1.  What is the difference between looking up the customer id and relating it like you mention?  Is the lookup field the issue or is the issue that I am using a Text Formula field in the relationship?  Could I create a new field and use the ToText function to get around this?

Can you help me on how I would go about doing #2?  I prefer that a button would not have to be clicked if possible.  It would be good if it could run after the table is updated in the middle of the night.