Welcome to the Babble!
Glad to have you join the forum, a great place to learn and share.
You ask some good questions that most newbies face.
A broader name as the actual domain name doesn't hurt too much, especially if you want to expand the content of your site as time goes along. For instance, my financial site is NOT named "achieve-financial-success" but that is my secondary keyword now and it is similar. My site covers all the basics of personal finance now but at first it covered mostly getting out of debt. A name that focused on that would have been a bit better at the beginning but it would have limited me later.
If you intend to focus on a specific niche and have a name that fits it you will do better and that is a recommended approach. But many have domain names that relate to nothing and are extremely successful (google, amazon, etc.). There are a couple hundred factors that are used to determine your placement on search engines so no one thing is an absolute.
As far as the about page and the like, all of them help, but the real essential is to develop a site that has lots of valuable content. The one thing I question about your thinking is something that can really hold you back but shouldn't. There will always be people who know things you do not know, but even now you will know some things that some others do not. Write for them.
If you keep studying and researching your topic, in a few months you will know more than almost all your visitors. Do not write about anything off the top of your head without informed information. Write (with research as needed) about what you can determine to be correct and keep adding to your content as you go. You can do just as well as any of the experts you see out there and if you study a bit you will soon be as well informed as any of them.