Dropshipping in India

hi, am going to start a new website and am registered under GST. customer comes to my website & places an order & pays for the item (say Rs 150), I pay the supplier (say Rs.100) & ask him to dropship it. The supplier is in India, but in a different state than mine. The customer can be in any Indian state (not looking at international market right now). now, i have few questions. can you please help me with it? 1. The supplier allows me to pay him in two ways, Rs. 100 (without GST) or Rs. 105 (with GST) if I require a tax bill.Which one should I choose? 2. Should I charge Rs. 150 (without GST) to the end customer? or Rs.150 + 5% to the customer. 3. Should the 5% in the above point be 5% of Rs. 150 (selling price) or 5% of Rs. 50 (profit)? 4. The supplier says he can send the invoice to the end-customer with his GSTIN number. He will also include his sister company name (I assume end-customer will not be able to trace the origins) and also my company name. The amount will be same as what I charge the customer. Is this ok? Or can I just ask him to not send the invoice at all. Which is better? 5. How will the GST payment to the government work in these situations? God, I wish GST was simpler. Thanks a lot for your service.