Headings, headers are actually unseen messages between client browser and server.
I mean H1, H2, etc. - not meta data in the header element.
I'll check out the recommended reading.
(and the actual code in an image tag is "alt")
"keywords in first paragraph"
Not even remotely important. That wasn't a "fact" when it was first bandied about 10 - 15 years ago and "positioning content" in the source code became the "experts" mantra.
now you just seem snarky - i would be very surprised to learn that keywords in the first paragraph - or top content of a page - have no relevance to rankings.