No problem about the long comment, of course :). Nice little demo, too!
1) There is, but it's not exactly about the number of pages as much as it is about the total size of all of your published materials. For the free account, that's 200MB, which is enough to publish quite a bit. An important note: you're not at all limited to publishing one demonstration or visualization per page. What we're seeing at the link you posted is in fact a Cloud Notebook with just one output in it—your Manipulate. A published Cloud Notebook can have any number of things, like this. Please also note from the collapsed input cells in this example—for a sufficiently efficient Manipulate, you can set ContinuousAction->True to make it more "interactive" in the cloud (like this).
2) You can see it on your Cloud account page by navigating to (say) your recent files here. The continuous demo I linked just above is 4.4kB, so you could store about fifty thousand of them on a free/basic account.
3) On any paid Cloud account, any deployments last in perpetuity. On a free one, they last for 60 days from time of upload—and I do think that applies to your uploads of these sorts of demos. I understand that this might be a bit annoying, but the good news is... you can simply redeploy to the same URL and then the 60-day timer should start again!
As for the colorblind issue, it's something I admittedly ought to think about more so that my talks are accessible as possible. You can see all of the "named" color schemes at the Color Schemes guide, and I do think that it's true that none of these is both perceptually uniform and cyclic. (The Complex plotting functions do have special cyclic color functions available though; you can check them out in the ColorFunction section of their respective Options sections of their documentation.)
That said... I believe (off the top of my head) that those are cyclic because they use Hue, which... is cyclic, but is maybe not perceptually uniform? If you have an example of such a color map that I could look at, that might help (and maybe I could make it with Blend). In the meantime, maybe check out some more demonstrations about Hue here.
