If your domain page is just a landing page and you have 100+ internal pages. Does it matter that you target the interior pages for SEO rather than the domain page? In other words, will a higher SERP for the domain page increase or make it easier to rank for other pages or are they basically independent?

Promoting only the home pages is short sighted and VERY poor marketing.

To search ALL pages are "home" pages.

Promoting only the home pages is short sighted and VERY poor marketing.

To for search ALL pages...oh darn, too late.

I would have mentioned this, but in a much more "poetic" way, but I would rather not outshine Chris. So I'll dumb it down.

Page A is about 123, page B is about 456, and so on. They are all "related", yet I want page A found in the SERPs for "123", and page B found for "456", and so on.

You might want to get a link here and there to all your pages at one time or anther. Having a link to your internal pages will help them individually in the SERP.

I prefer to target SERP more on those subpage because subpage usually is those categories page and usually conversion is came from those page. That is why people target more on subpage before home page.
Home Page usually high bounce rate because sometime home page are not easy to navigate and search on what they want that is why turn to bounce rate compare to conversion rate.

A SERP may refer to a single page of links returned, or to the set of all links returned for a search query.

Complex question to be able to make you understand but I will do my best.

First of all, the short answer is yes. The way a website architecture is layed out, the site will naturally disperse your PR through your site. But to make this happen you need that PR starting on your homepage. For example (note 1st each page has its own PR) if I made one of my pages high PR this page would rank well, but my site would not. If you rank your site well, the PR will spread through other pages on your site and many pages will rank well. To go further into it, this is where internal linking comes in.

generally its like this eg: homepage PR4>categories>PR3 and so on. Now your homepage PR has actually given your category the PR3 without your categories getting any other links.

Complex question to be able to make you understand

No it isn't, it is THE MOST SIMPLE QUESTION POSSIBLE.

And your answer is totally wrong.

I agree with chishirts that, only tarted main page serp is very poor techniques for marketing. You have to use your landing pages as well beside only home page.