is there a way to carry forward the value of the salesrep (employee) from Sales Order to Purchase Order and Vendor Bill when dropshipping? We’d like to see Vendor Bills by the salesrep on the related Sales Order.

Yep, not by default, but you can carry it over with a simple script or workflow. Easiest way: create a custom field on the PO and Vendor Bill, then use a workflow or UE script to source the Sales Rep from the related Sales Order.