Hi,
In answer to question 1. No. you can not have different domain names pointing to different parts of the site. You can have different domains eg **** and mydomain.net all pointing to the same site, but they must be the same site.
Question 2. If all the subdomains are bits about you myhouse.**** and mycar.**** and mypics.**** that you maintain, are all linked to the top pages, then not a problem at all.
Andy