Should "most-trusted" be hyphenated?

I would suggest not, however I'd wait until somebody verifies my answer of disagrees with me to be sure. There are plenty of proof-readers on the site who are more informed on such matters.

Yes.
The two words are working together to modify Web site.

It's a toss-up. I was taught (a hundred years ago) that with constructions like this (well-built, even-tempered - that is, short adverbs modifying the adjective), use the comma if it comes before the noun and omit the comma if it follows. It's one of those "rules" that becomes more "convention" than anything based on logic. I still follow the suggestion.

[Mary is well educated ~ Mary

I would follow Grammar Geek's answer. This is her field of expertise and who I hoped would answer your post.

Philip[Mary is well educated ~ Mary is a well-educated young lady]

That's it exactly.

She attends school part time. She's a part-time student.
The event was well attended. It was a well-attended event.
Her car is neon green. She has a neon-green car.

etc.