You should be able to run a second tinydns instance trivially. But if they're on the same server, doesn't tinydns bind to everything?
There's lots out there on tinydns, including answers to this question. http://djbdns.faqts.com
is a good starting place (check out the links and tutorials there), but also check out http://tinydns.org
You've understood the catch22 in ns1.something.com being a nameserver.com - it *is* a catch22. The way you can do is to register a "child nameserver" with the registrar that registered something.com. The TLD roots then return the IP for ns1.something.com when someone asks for the delegation (returning it as what's known as "glue").