Vinica means vineyard in Slovak and if such places have or had in the past real vineyards, all is clear. The other possibility is in the natural changing words by people who got used to say certain words and they are slowly changing the name of another, mostly archaic word, which has a completely different meaning, but sound very similar. So, few vinicas could have something in common with Wends.
As for the Morava toponyms, there are two explanations I've heard about. Moravá rieka means a swamp river in Slovak. The other one is that Morava originates in the Goddess Morena/Mara.. yeah, you pointed out many other examples of this word, it's important that everywhere there live/d the Slavs. We know examples when our ancestors called parts of the nature by Slavic Gods and Morava as a really ancient name doesn't have to be any exception. That's it.