I like the idea to allow consumers to directly buy from manufacturers. But, how is the system decentralized when consumers are buying from manufacturers and there's still a link in the chain which are the fulfillment centers who can influence the price because they need to be payed as well ?

Yep, and in WP : fulfilment centres will not be allowed to markup prices, they will be paid for the fulfilment process only.

You'll be able to sign in to your personal investor's account to buy INS. At this platform you will deposit your altcoins, and when the tokensale is active you'll be able to buy INS tokens for ETH. The platform uses Coinpayments exchange rates to convert your altcoins to ETH. Conversion happens at the moment you buy INS.

Yes, in INS they are going to take fiat, ETH, BTC, and, of course, INS tokens will be the main means of payment within the INS Ecosystem.

-Once a person enters our site via your referral link and creates an account, he becomes your referral and receives a 1% bonus for all his purchases.
-You’re eligible to receive 5% of every token purchase made by your referral.
-Payment is made in INS tokens. Tokens will be distributed after the end of the ICO.
-You can keep track of your referrals and see how many tokens you get from their purchases.
https://blog.ins.world/ins-ico-referral-program-5-a64353c6ae64

Tokens will be issued 14 days after the end of ICO.

Yes. And When placing orders via the INS website or app, consumers will be able to specify delivery details and complete purchases using onsite payment.
https://blog.ins.world/a-decentralized-online-grocery-marketplace-how-it-works-for-consumers-290702184f40 

Hey, guys! Will your tokens be available on exchanges??

Oh, so soon. We need to hurry up!