Tree of Indo-European Languages (image)
upload.wikimedia.org
upload.wikimedia.org
Edit: forgot vod people, also called krevingi, they still existed in the end of the 19th cent, few families.
But, seriously, I'm impressed with your very knowledgeable answer. It's very interesting.
Defining what makes a language a language is a very political issue, but there are some standard ways to judge. The half-joking criteria is whether it has an army and navy. Another is mutual intelligiblity—can speakers of a different "language" understand it and be understood by native speakers?
And as a musician, it modestly terrifies me that there is an entire language branch/split based on aoelian vs. doric.