You should be able to access your whole iTunes music library. Of course, Home Sharing has to be turned on in iTunes (File > Home Sharing) and iTunes must be running.
On the iPad, as you say, Settings Music > Home Sharing must be Set up.
If all this is good you should be able to access Home Sharing by touching the More button at the bottom of the iPad Music screen. This should bring up a selection with Shared as one of the choices. Touching Shared gives you the choice of My iPad or <your name> Library. Touch <your name> Library and the Music App should show (slowly perhaps) everything in your shared Music Library.
Where is this going wrong?