Sales Team not flowing through to Invoice

Our system is currently not selecting the default sales team listed on the sales orders for our sales and therefore our forecasting capability is for naught.

To create invoices we select the transaction menu item, "invoice billable customers", then invoice for each item for each customer.

Is this the correct method?  Per all the documentation I am reviewing the sales person that was on the original opportunity and sales order should also be on that invoice.

EDIT UPDATE:

We are also not seeing any of the following SO items flowing through to the invoice:

Opportunity
Department
Class
Location 
Due Date