> The moment you create your own content (even if you are a content provider yourself) you lose the protection of Section 230.
No. Practically every social network and publisher creates their own content occasionally, yet there's plenty of precedent for companies like Google, Ebay, Amazon, Apple, and Facebook being protected under Section 230.
A better, more accurate way of phrasing your objection would be to say, "Section 230 does not protect you from lawsuits over the specific content you created." So if Twitter's company-written annotation was found to be libel, they could of course be sued over that.
But adding your own content to a forum/platform has no bearing on whether Section 230 applies more broadly to other content that you host. Take a deeper look at your example:
> You cannot make a list of "staff picks" and then claim that the content comes from other sources
This is exactly what Amazon, Apple, and Google Play do every day. And all of those platforms have been ruled to be protected by Section 230 in multiple lawsuits -- covering everything from trademark violations to defective products. The fact that Amazon has a "recommended brand" section does not mean that they are liable for everything that shows up on their store. And that's a principle that's held up in real courts over, and over, and over again.
> Editing/policing content
I don't want to keep beating the same horse, but that's not what Twitter did. They didn't edit Trump's tweet or restrict it, they added their own speech next to Trump's tweet. That has nothing to do with Section 230, it's just a generic, common case of 1st Ammendment protected counterspeech.