Packaging powdered foods before shipping to fulfillment center

Seems to me you would find a supplier that meets your needs. It maybe cheaper to buy in the drums, but add the expensive of delivering to packaging, paying for packaging and then delivery state side, and is it really cheaper than buying the goods the way you want it?

The big companies likely make the capital investment to bring the packaging in-house. That way they have full control over process and costs.

The US FDA likely has regulations that apply here and I wonder about multiple moves of the product prior to entering the US. The google searching I did for a minute or two while answering this question didn't bring up anything super relevant, though.

The Warrior Forum is simply not the place for this kind of expertise. This is primarily an online marketing forum. You might try asking in the Offline subforum (yes there are other subforums here!) but I doubt there is anyone there with direct experience despite that being the home for the "real" business owners on the forum.

I recommend you go to an expert platform like clarity.fm and check there. A search on Clarity for "food packaging" brought up several subject matter experts I'd consider talking to--based on my very limited experience in the field and broad experience in life (ie. someone to talk to who had not just started a bakery but had real industry experience.)

Investing $50 or $100 on a call or two could be very valuable to you, and it's surely a tax-deductible expense.

EDIT: I also recall an episode of The Profit with Marcus Lemonis where they went on a tour of a food packaging plant in Chicago. Marcus will often take a struggling business owner on a tour of a successful version of their concept, so they get the idea of what's possible. A google search for "food packaging companies chicago" or "co-packing" got some interesting results.