Amazon can be the big bad wolf to the internet like Walmart is to brick n mortars. But I personally love them both because we as a small business have something that neither of them do not have, speed of getting products in house. When they run out of products, it can take months before amazon will get them in again and that is where the small business can take over the listing, well at least for awhile. (If amazon is my competitor with the listing, I do not send it FBA.)
Barcodes: It is different with every catagory, meaning with sporting goods, you need a upc. With Jewerly, no upc required and with like sewing/crafts you can request no upc and usually get it.
Pictures: If you have a product on amazon and amazon starts selling it, replace your picture to a crappier one or the manufacturers, wait a week and then remove the listing. They do not have your good picture anymore.
Personally I do not put all of my eggs in one basket. It can take years before google gets your listing to #1 organically (and then google changes the rules again) whereas amazon is instant cash and has many many eyes.
Just think outside the box and study the top sellers, remember not everyone is selling at cost.
Good luck and happy selling.