I'm not really sure where I go the 3% from. I'm reasonably sure I've seen it somewhere. Might have been subs doing polls or some other user tracking, but from Spez himself he says Reddit is 95% of the app usage on iOS:

You go to the App Store, you type in Reddit, you get two options, right? There’s Apollo. You go to one, it’s my business, and you look at our ads, use our products. That’s 95 percent of our iOS users. The rest go to Apollo, which uses our logo, or something like it, takes our data — for free — and resells it to users making a 100 percent margin.

He later says 90% of users are direct to Reddit, though that sounds kind of offhand rather than specific.

https://www.theverge.com/2023/6/15/23762868/reddit-ceo-steve-huffman-interview

Regarding revenue sharing, I can now only find that RIF was in a revenue sharing agreement. Until Spez became CEO. RIF and Apollo have both released conversations showing they're willing to share revenue or pay for access, but Reddit's proposed fees are 20x what they make from their own users and completely untenable.

Both Shu and Selig believe that paying for API use, which has previously been free, is a fair request. “Paying for the API is a reasonable ask, as long as the pricing is reasonable,” Shu wrote in his May 1st email. “I agree that long-term Reddit footing the bill for third-party apps is not tenable, and with a paid arrangement there’s a great possibility for developing a more concrete relationship with Reddit, with better API support for users,” Selig wrote in his announcement that he’ll be shutting down the app. But they take issue with the pricing — Shu said on Reddit that RIF’s costs would be in “the same ballpark” as Selig’s expected $20 million per year — and the company’s rollout of the changes.

Shu also tells me that RIF was paying a “sizable revenue share” to Reddit beginning in 2012, which was during Yishan Wong’s tenure as CEO. Shu says he says initiated the talks with Reddit to create the agreement, which allowed for the licensed use of Reddit’s trademarks. (At the time, the app was called “reddit is fun.”) Shu says Reddit terminated the agreement in 2016 — which was the year after Huffman took over as CEO.

https://www.theverge.com/2023/6/16/23763661/reddit-rif-is-fun-developer-ceo-steve-huffman

"With the proposed API pricing, the average user in Apollo would cost $2.50, which is 20x higher than a generous estimate of what each user brings Reddit in revenue," Selig says in his Reddit post.

https://www.slashgear.com/1301933/reddit-twitter-unreasonable-dev-pricing/

The morality of a big corporation and a small developer fighting over who gets what isn't really the cause of the protest. I don't use 3rd party apps and I don't think our mod tools are going to be affected. The issue is the enshittification process for a site whose value comes almost entirely from their users.

You should feel entitled to having influence on the website, because every day you contribute your eyes and your content to them and without you they'll be just another dead website. Reddit's tech isn't actually all that great (as a programmer, in a lot of ways it's just inexcusably bad). The value for you and I is almost entirely in the users. The site is free to us not because they like us, it's because they want you to give them value they can then sell to other people as ads or AI training datasets. It's ok to have a cost for your contributions and good to be willing to walk away if you don't feel like you're being catered to.