How to best host and publish art and writings online, and protect them?

I want to help my father publish a short story, a play, and some chapters of his novel (if not the whole thing).

My aims:

1) My initial idea is to build a simple blog and host the writings as html pages. But I want to make sure in advance, should he decide to publish this same work in another medium in the future, is a certain Creative Commons license or copyright required to protect the work somehow? In the world of paper manuscripts, a handy and cheap way to copyright your work was to post the work in a self-addressed envelope - the postal service sort of notarizes it with their postmark along with the date- and not open it.

2) Curious about self-publishing. Is this what people are using Patreon for nowadays? I'm a bit too hesitant to put this in Amazon's self-publishing domain, as it stands. Does anyone have experience with this?

3) I also want to host photos of his paintings online, but I want to protect them somehow. I have not put them on Instagram or anything like that, because in my view, then Facebook owns the content. Another thought is Photoshopping in watermarks on the photos, but is that still useful somehow? I just don't want to do something wrong, and find out 10 years later some studio is selling prints of these without crediting the artist, and this is not my domain, which is why I'm seeking your help.