sold-to and ship-to business partners

SAP Business One 9.2.

We sell products to a distributor (sold-to and bill-to, has resell certificate), but was asked to ship to several end-users. The end users are also our customers (a BP) and some of their employees in the same or different branches also buy (sold-to), receive (ship-to) and pay (bill-to) directly with us.

1. Can we set the end-user company the same BP - either they order from the distributor or from us directly?

2. Distributor situation: Sold-to and ship-to are different BP, How to link them in SAP business one in a sales order?

3. Sales tax situation, If end-user (also our BP) buys from distributor (has resell certificate), we don't collect sales tax, but we collect sales tax if BP buys directly from us.

Thank you for your help in advance.

SW