Rush is not advocating a third political party for conservatives, but rather for democrats, because it's a good way to weaken democrats and liberals at election time. Rush makes this very clear in the comments you posted:
Don’t you think that’s why I posted that specific paragraph?
Right. Actually, those who know Rush, know he likes to illustrate the absurd by being absurd. This comment was pretty much a joke, and he was making fun of the liberals. I listen to Rush everyday, I know he is against the idea of a conservative third party.