"Microsites and other domains I ownthat link or redirect back to my site will help my SEO."
The chances of this doing much for your SEO are slim to none. It’s like having an election in which you vote for yourself a thousand times -- that still counts as one vote.
Search engines are smart enough to know who the registrants are for a domain and can see if it’s the same person as your primary domain. (Note: If you are reading this and thinking, “Well, then I’ll just change my registration information,” you are clearly thinking like a spammer. Don’t be that person!)
Unfortunately, those who strive to have lots of pages on their website also tend to overlook the quality of that content -- and realistically, it’s difficult to strive for both. The aim should be to publish what is most relevant. Have your content be at its best.