Turning customers away/charging more for a certain product

Assalaamualaikum. I have a sweet bussiness and a big part of my bussiness is supplying hawkers. Their is a certain product(Mielie Pop) which is in demand and neither myself or my competitor are able to get a good enough supply of the product in order to meet the demand. Some of the hawkers only buy this item and nothing else and it leaves me short at times when trying to keep supply for my regular customers.

Q1. My competitor has a policy that if customers don’t buy anything else from his shop besides this item he charges them a higher price,can this be done according to shariah as it forces people to purchase other items as well?

Q2. Would I be wrong if I turned customers away who only buy this item in order to keep it for my regular customers who buy other things from me as well?

Q3. Selling products like ntsu/snuff is this permissible?
Jazakallah.