"But despite all the missteps and stress, the results might justify all the pain. I expected the new website to increase sales by 10-20%, but it’s been closer to 40%."

Should have put this in the beginning of the article.

As for all the issues mentioned in the article, trust me on this, it's always like this. I've been that "small client" hiring externals at all tiers: mechanical turk, freelancers, agencies.

You ask for A but get B. You agree on a timeline but none are respected. You can put your foot down but that does absolutely nothing, they don't need you. You're more like a hobby on the side.