I can see in the database table.column custinfo.cust_salesrep_id . This only allows for 1 sales rep per customer. Is there another path that would allow for multiple sales reps per customer?
What edition do you have? the Dist edition has the concept of inside sales rep, the sales rep that took the order.
There is also an enhanced commissions package as well.https://xtuple.com/products/add-ons/enhanced-commissions