Wrote a blog post for Myths and Legends Day on the A to Z main blog. It's about how to find good books on legends and mythology 
And what to look for in a good source.
Read here
http://www.a-to-zchallenge.com/2023/10/happy-myths-and-legends-day.html?m=1
I love your list, but I want to add a "hot take"...
... how much one should believe of a source, & how to proceed in using it, depends (in my opinion only), on how one intends to use it.
If I'm planning to write a (semi)academic treatise on something, sure, I need to be careful af.
But if I'm writing e.g. a "pop-mythology" booklet, or a fun Mastodon post (hehe), I don't feel it is necessary or even useful to be too deep.
Or maybe I'm wrong!
@mythologyandhistory I wouldn't say deep, but I'd still want to be accurate, unless I'm doing a creative take 
I agree that accuracy is wanted, but it's not always really possible (or so I've found).
Sometimes, I decided to go with the "most common opinion" in e.g. a Mastodon post, because I would need to write a lot of "allegedly"s & "possibly"s otherwise :P
I try to get more accurate if someone challenges the notion. It's actually a really neat way to have conversations here!