A few points:
1) Amazon is not a monopoly in any sense of the word. They are not the only provider of any service in any area, in fact, they are not even > 50% in any particular market segment be it cloud or retail, or even the subsection of retail that is online sales. Amazon operates in a lot of markets, that makes it a large conglomerate, but not a monopoly. Also, the more markets Amazon enters, the *better* it is for consumers in those markets due to increased competition.
2) Even if Amazon was a monopoly that's not sufficient to "break it up". They have to harm consumers (which they are not doing since consumers are largely benefiting from the anti-inflationary effects Amazon has on prices, and the convenience of it's operations) and/or they have to inhibit competition, which they are also not doing. Anti-trust laws aren't there to protect employees.
3) Amazon coming up with their own products based on their market data (from operating a retail marketplace) IS the exact same thing as Walmart's "Great Value" brand or Costco's "Kirkland" brand (and soon probably Uber with Ubereats, etc.). They use the their marketplaces to research products and see if they can easily build a comparable product for cheaper. This isn't' against the law and is helpful to consumers by promoting competition and lowering prices.
4) I've worked in an Amazon warehouse (aka a Fullfilment Center), as every Amazon employee had to do when I joined, I never had a problem going to the washroom. Yes, this is anecdotal and it was just a one week stint rather than a full time job. Yes, it was hard, but I didn't see anything inhumane. It was also much easier than other jobs I have done in the past (other warehouses as a teenager, painting in hot houses, roofing, etc.)
5) Amazon is working very hard on replacing all of the warehouse workers and drivers with machinery/automation (I worked in this area), so these complaints about working conditions should be impacting less folks as time goes on.
6) Finally, the malls. Amazon purchasing the space and making them productive seems like a good idea to me.