Dropship Store already ready.

I already build one drop-Shipping Store. i am using woo-commerce theme. I need some help with my Business setup and i have some Quarry.

If anyone one can give me suggestion it will be great..

1. How i manage my Invoice serial number ? Any plugin?
2. How i manage 24/7 customer email support?
3. How i ignore more dispute?
4. What payment gateway should be best for USA market?
5. How can i Find winning product?
6. How can i generate pdf purchased receipt to my customer email?
7. How can i make more $$$ with less Facebook Ads.
8. How do i find USA wholesaler?
9. How can me and my Customer track orders from my website.
Kindly let me know if anyone know any of these Question. I am Totally New So thats why I am asking too many question.

Thanks
B&R

use the ePacket plugin to find USA dropshippers
Stripe Payment is mostly like good for US buyers
sort aliexpress product by new and more orders to find winning orders

questions 1 & 6 - search for the invoice plugin from yithemes - will be more then what you need.
question 2 - use a ticketing plugin for wp and setup automatic emails for the time when you're not online.
question 9 - you can't track orders, if your suppliers use multiple shipping companies. I can recommend you using wp cargo to create the orders inside your site and you will update them from the shipping company, this way your customers will see it on your website. Other option is to ask your suppliers how would they ship the products and you can try to find a solutions that specific companies.
question 7 - this depends on the quality of your ads, the quality of the products you're selling, but if this is the first time you're doing fb ads, would be hard and you will past thru a trial and error process. With time you can gather a good audience in fb and from there ads can become more cheaper - if you know how to use it

question 3 - check the products yourself, choose only the good quality products, make sure you verify and show the delivery time to your clients.

rest of the questions have an answer above.