Getting DMOZ to link to each site, as long as they are different content, has been pretty easy as long as you meet their guidelines...that gives you all of those incoming links (in addition to any LLs that link to those free sites) and then each site should also have a pointer to the root (which it sounds like you are already doing) with good text...not just "more links here"
as far as the hundreds of domains...it takes quite a while to build up each one if you go that route....and yes each domain (in my case) has free sites underneath the root...its taken a few years and Im no where near finished
- a small disclaimer though...I tend towards the "keyword domains" out of old habits, so I usually use a domain for a niche...and then build a LL/hub that links them together in that niche. There are a few that arent done that way and as long as you have good incoming links, it shouldnt matter though - a branded domain works just as well...although I try to do both branding and keywords on the same domains (just superstitious)