The page that you reference describes how to configure a domain hosted
on the Google Talk Service. The page does not apply to you because you
are hosting the domain on your own server.
My guess is that you probably want SRV records like this:
_xmpp-server._tcp.genphysics.com. IN SRV 5 0 5269
wildfire.genphysics.com.
_jabber._tcp.genphysics.com. IN SRV 5 0 5269 wildfire.genphysics.com.
The Wildfire Support Forum is a good place to ask questions about
Wildfire configuration. See
http://www.igniterealtime.org/forum/forum.jspa?forumID=40 .